ICES WGSPEC REPORT 2012
SCICOM S TEERING G ROUP
ON
E COSYSTEM F UNCTIONS
ICES CM 2012/SSGEF:10
R EF . SCICOM
Report of the
Working Group on Small Pelagic Fishes, their
Ecosystems and Climate Impact (WGSPEC)
27 February – 2 March 2012
Fuengirola, Spain
International Council for the Exploration of the Sea
Conseil International pour l’Exploration de la Mer
H. C. Andersens Boulevard 44–46
DK-1553 Copenhagen V
Denmark
Telephone (+45) 33 38 67 00
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Recommended format for purposes of citation:
ICES. 2012. Report of the Working Group on Small Pelagic Fishes, their Ecosystems
and Climate Impact (WGSPEC), 27 February – 2 March 2012, Fuengirola, Spain. ICES
CM 2012/SSGEF:10. 63 pp.
For permission to reproduce material from this publication, please apply to the General Secretary.
The document is a report of an Expert Group under the auspices of the International
Council for the Exploration of the Sea and does not necessarily represent the views of
the Council.
© 2012 International Council for the Exploration of the Sea
ICES WGSPEC REPORT 2012
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Conte nts
Executive summary ................................................................................................................ 1
1
Opening and Agenda .................................................................................................... 2
2
Introduction .................................................................................................................... 2
3
2.1
Terms of Reference ............................................................................................... 2
2.2
Small pelagic fishes and climate impact ............................................................ 2
2.3
Climate indices ...................................................................................................... 3
2.4
Development of working group meeting .......................................................... 4
Case studies .................................................................................................................... 5
3.1
Long Term Variability of the Canary Current Upwelling System ................. 5
3.2
NAO related small pelagic fisheries fluctuations off Morocco and
Senegal ................................................................................................................... 8
3.3
Historical landings of small pelagics off North West Africa.
“Signals” of the climatic effect on small pelagics in North West
Africa and in the Canaries ................................................................................. 13
3.4
Decadal changes in sardines and anchovies in the Canary Current
Upwelling System ............................................................................................... 17
3.5
Overview of large and meso-scale oceanographic processes
relevant to the Gulf of Cádiz ............................................................................. 19
3.6
Small pelagic fish research in the Mediterranean by the Spanish
Institute of Oceanography: available data series for a climatic
analysis ................................................................................................................. 25
3.7
Environmental impacts on anchovies; sardines and sardinellas in
the north western Mediterranean ..................................................................... 31
3.8
Population dynamics of small pelagic species in the Adriatic Sea:
Stock Assessment Models and Environmental Factors ................................. 33
3.9
Biomass evaluation of anchovy (E. encrasicolus), sardine (S.
pilchardus) and sprat (S. sprattus) in the western Adriatic Sea by
means of acoustics and preliminary analysis of possible
relationships with environmental parameters ................................................ 35
3.10 Impact of climate variability on small pelagic fishes in the Eastern
Mediterranean ..................................................................................................... 38
3.11 Anchovy: environment, biology and recruitment in the Bay of
Biscay .................................................................................................................. 39
3.12 Impact of climate variability on herring and capelin in northern
seas
.................................................................................................................. 41
3.13 Impact of climate variability on North Atlantic plankton ............................ 45
3.14 Identifying drivers for zooplankton variability: the genetic
programming approach ..................................................................................... 46
4
Results and intersessional activities ........................................................................ 49
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ICES WGSPEC REPORT 2012
5
Elections, place and dates of the next meeting ....................................................... 49
Annex 1: List of participants............................................................................................... 50
Annex 2: Agenda................................................................................................................... 55
Annex 3: Draft terms of reference for the next meeting ................................................ 58
Annex 4: Cycles, trends, and residual variation in the Iberian sardine
(Sardina pilchardus) recruitment series and their relationship with the
environment.................................................................................................................. 59
Annex 5: Small pelagic fishes and zooplankton in Belgian waters ............................ 60
Annex 6: Vital rates of pelagic fish larvae (VITAL) ....................................................... 62
Annex 7: Changes in the location and extent of North East Atlantic
mackerel catches: possible fishery and climate change effects ........................... 63
ICES WGSPEC REPORT 2012
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Executive summary
Small pelagic fishes such as sardine, sardinella, anchovy, herring, sprat and others
represent about 20–25 % of the total annual world fisheries catch. They support important fisheries in many European countries. Their dynamics have important economic consequences as well as ecological ones. The great plasticity in the growth,
survival and other life-history characteristics of small pelagic fishes is the key to their
dynamics and makes them ideal targets for testing the impact of climate variability
on marine ecosystems and fish populations. North Atlantic marine ecosystems are
exposed to large-scale climate forcing by the North Atlantic Oscillation (NAO) on the
decadal and by the Atlantic Multi-decadal Oscillation (AMO) on the multi-decadal
scale, in addition to global warming. At present, a fascinating natural climate experiment involving small pelagic fish is going on in waters surrounding Europe,
which has been largely ignored, in spite of its acute and future commercial importance for the European fishing industry. Numerous observations by European fishery
scientists over the last 20 years demonstrate clearly that small pelagic fish populations in all shelf seas surrounding Europe from the North African upwelling and the
Black Sea in the south up to the Baltic Sea and southern Norwegian coasts are shifting
their distributional borders to the North with concomitant dramatic changes in
abundance and recruitment. Spectacular examples are the invasion of the North Sea
by anchovies and sardines since the mid-1990s which have established spawning
populations in this northern shelf sea or the northward migrations of sardinella in the
Mediterranean. Another example is the drastic increase of the Baltic sprat stock
which was initiated in the late 1980s. To develop scenarios for future fluctuations of
small pelagic populations, it is necessary to understand the climatic background of
their fluctuations in the past. During the meeting, 12 case studies on long-term fluctuations of small pelagics from ecosystems spanning from the upwelling region off
NW Africa to the Nordic Seas, including the Mediterranean, were presented and potential links with climate variability were discussed. The WG focused on the impact
of the AMO during the 20th century. Apparently, many of the populations studied
show population swings in synchrony with the warm and cold periods of the AMO,
so displaying clear reactions to multi-decadal climate forcing. These studies will be
continued during the intersessional period and result in a joint publication.
The meeting was attended by 26 scientists from 10 countries, including physical
oceanographers, zooplankton experts and fisheries scientist. The close cooperation
between scientists from the ICES area and from the Mediterranean proved to be
highly successful and should be taken as an example for future collaboration between
ICES and the General Fisheries Commission for the Mediterranean (GFCM) both of
which have recently signed a memorandum of understanding.
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1
ICES WGSPEC REPORT 2012
Opening and Agenda
The second meeting of WGSPEC took place on 27 February – 2 March 2012 at the
Centro Oceanográfico de Málaga (Fuengirola, Spain) of the Instituto Español de
Oceanografía (IEO). The meeting was opened by the chairman of WGSPEC (Jürgen
Alheit). The local host was Alberto Garcia. The meeting was attended by 26 scientists
from 10 countries (List of participants: Annex 1). The agenda is given in Annex 2.
2
Introduction
2.1
Terms of Reference
a ) Review the outcomes from the workshops WKAMO and WKNORCLIM;
b ) Investigate the impact of climate variability and change on small pelagic
fish populations (anchovy, sardine, sardinella, herring, sprat) in the area
from NW Africa to the Barents Sea, incl. the Mediterranean, for the period
from mid-1900s to the present;
c ) Suggest relevant joint theme sessions and workshops for ICES and PICES
which are also relevant to ICES assessment working groups on pelagic
fish;
d ) Prepare contributions for the 2012 SSGEF session during the ASC on the
topic areas of the Science Plan.
2.2
Small pelagic fishes and climate impact
Small pelagic fishes such as sardine, anchovy, herring and others represent about 20–
25 % of the total annual world fisheries catch (Hunter and Alheit 1995). They are
widespread and occur in all oceans. They support important fisheries all over the
world and the economies of many countries depend on those fisheries. They do respond dramatically and quickly to changes in ocean climate. Most are highly mobile;
have short, plankton-based food chains and some even feed directly on phytoplankton. They are short-lived (3–7 years), highly fecund and some can spawn all yearround. These biological characteristics make them highly sensitive to environmental
forcing and extremely variable in their abundance (Hunter and Alheit 1995). Thousandfold changes in abundance over a few decades are characteristic for small
pelagics and well-known examples include the Japanese sardine, sardines in the California Current, anchovies in the Humboldt Current, sardines in the Benguela Current
or herring in European waters. Their drastic stock fluctuations often caused dramatic
consequences for fishing communities, entire regions and even whole countries.
Their dynamics have important economic consequences as well as ecological ones.
They are the forage for larger fish, seabirds and marine mammals. The collapse of
small pelagic fish populations is often accompanied by sharp declines in marine bird
and mammal populations that depend on them for food. Major changes in abundance
of small pelagic fishes may be accompanied by marked changes in ecosystem structure. The great plasticity in the growth, survival and other life-history characteristics
of small pelagic fishes is the key to their dynamics and makes them ideal targets for
testing the impact of climate variability on marine ecosystems and fish populations
(Hunter and Alheit 199?).
North Atlantic marine ecosystems are exposed to several large scale climatic forcings,
such as the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation
(AMO) and global warming. The interdependence between these different climate
ICES WGSPEC REPORT 2012
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indicators and their individual as well as their combined impact on marine ecosystems are extremely poorly understood. At present, a fascinating natural climate experiment involving small pelagic schooling fish, such as sardines, sardinellas,
anchovies, herrings and sprats, is going on in waters surrounding Europe, which has
been largely ignored, in spite of its acute and future commercial importance for the
European fishing industry. Numerous observations by European fishery scientists
over the last 20 years demonstrate clearly that small pelagic fish populations in all
shelf seas surrounding Europe from the North African upwelling and the Black Sea
in the south up to the Baltic Sea and southern Norwegian coasts are shifting their distributional borders to the North with concomitant dramatic changes in abundance
and recruitment. Spectacular examples are the invasion of the North Sea by anchovies and sardines since the mid-1990s which have established spawning populations
in this northern shelf sea (Beare et al. 2004a,b; Alheit et al. 2012; Petitgas et al. 2012) or
the northward migrations of sardinella in the Mediterranean (Sabatés et al. 2006; Tsikliras 2008). Another example is the drastic increase of the Baltic sprat stock which was
initiated in the late 1980s (Alheit et al. 2005).
All these dramatic changes in distribution and abundance of small pelagics seem to
be associated with recurrent climatic events or periods, oscillations, rather than with
global warming. The late 1980s, when the Baltic sprat exploded and, similarly, sudden changes on other trophic levels in the central Baltic were recorded, were characterized by a sudden increase of the NAO index, a climatic signal which also was
reflected in the dynamics of other European shelf sea ecosystems and even in northern and central European freshwater lakes (Alheit et al. 2005, Alheit and Bakun 2010).
Anchovies and sardines started around the mid-1990s to extend their northern distribution limits into the entire North Sea, several years after the increase of the NAO
index. Apparently, they had been spawning there already in the 1940s and 1950s, but
disappeared again in the 1960s. Interestingly, from about 1930–1960 and again since
the mid-1990s, the AMO, which represents North Atlantic water temperature, has
been in a positive phase. Consequently, invasion of anchovies and sardines into
North Sea and Baltic seems to be associated with the dynamics of the AMO (Alheit et
al. 2012).
2.3
Climate indices
The North Atlantic Oscillation (NAO) is the leading pattern of climate variability
over the North Atlantic and adjacent continents (Hurrell and Deser 2010). The NAO
refers to a redistribution of atmospheric mass between the Arctic and the subtropical
Atlantic. Atmospheric impacts of the NAO include substantial changes in surface air
temperature, wind direction and speed, storminess and precipitation. Ocean impacts
include changes in heat content, gyre circulations, mixed layer depth, salinity, high
latitude deep water formation and sea ice cover. The NAO index (NAOI) switches
between positive and negative phases. Over northern and central Europe, high (low)
index values are associated with increased (decreased) westerly winds, milder
(cooler) temperatures and increased (decreased) precipitation. In contrast, over the
Mediterranean, a high (low) NAO index is associated with less (more) precipitation.
The Atlantic Multidecadal Oscillation (AMO) reflects multidecadal warming and
cooling periods of the North Atlantic and its index are linearly detrended SST anomalies (Ting et al. 2009) between 0–60°N with a 60–80 years cycle (Kerr 2005). It seems to
be reflected by the occurrence of Sahel zone drought, variability in North East Brazilian rainfall, and North American climate (Knight et al. 2005).
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2.4
ICES WGSPEC REPORT 2012
Development of working group meeting
During the meeting, a large number of case studies from different stocks of small
pelagics and their ecosystems was presented and discussed (Table 1). Statistical
analyses were started but there was not sufficient time to finish them. Consequently,
it was decided to continue these analyses during the intersessional period and aim
for a joint publication on the results. Draft terms of reference for the 2013 meeting can
be found in Annex 3.
References
Alheit, J., Bakun A. 2010. Population synchronies within and between ocean basins:
Apparent teleconnections and implications as to physical–biological linkage mechanisms. Journal of Marine Systems, 79, 267–285.
Alheit, J., Möllmann C, Dutz J, Kornilovs G, Loewe P, Mohrholz V, Wasmund N.
2005. Synchronous ecological regime shifts in the central Baltic and the North Sea in
the late 1980s. ICES Journal of Marine Science, 62, 1205–1215.
Alheit, J., Voss R, Mohrholz V, Hinrichs R. 2007. Climate drives anchovies and sardines into North Sea. GLOBEC International. Newsletter, 13 (2), 77-78.
Alheit, J., Roy C, Kifani S. 2009. Decadal-scale variability in populations. In: Climate
Change and Small Pelagic Fish (eds Checkley DMJr, Alheit J, Oozeki Y, Roy C), pp 6487. Cambridge University Press, Cambridge.
Beare, D., Burns, F., Greig, T., Jones, E., Peach, K., Kienzle, M., McKenzie, E., Reid, D.
2004a. Long-term increases in prevalence of North Sea fishes having southern biogeographic affinities. Mar. Ecol. Prog. Ser. 284: 269-278.
Beare, D., Burns, F., Jones, E.,., Portilla, E., Greig, T., McKenzie, E., Reid, D. 2004b. An
increase in the abundance of anchovies and sardines in the north-western North Sea
since 1995. Glob. Change Biol. 10: 1209-1213.
Hunter, J R, Alheit J. 1995. International GLOBEC Small Pelagic Fishes and Climate
Change program. GLOBEC Report No. 8.
Hurrell, J., Deser, C. 2010. North Atlantic climate variability: The role of the North
Atlantic Oscillation. J. mar. Syst. 79: 231-244.
Kerr, R.A. 2005. Atlantic pacemaker for millennia past, decades hence. Science 309:
41-43.
Knight, J.F., Allan, R.J., Folland, C.K., Vellinga, M., Mann, M.E. 2005. A signature of
persistent natural thermohaline circulation cycles in observed climate. Geophys. Res.
Lett.: 32, L20708.
Sabatés, A., Martín, P., Lloret, J., Raya, V. 2006. Sea warming and fish distribution:
the case of the small pelagic fish, Sardinella aurita, in the western Mediterranean.
Global Change Biology 12: 2209-2219.
Ting, M., Kushnir, Y., Seager, R., Li, C. 2009. Forced and Internal Twentieth-Century
SST Trends in the North Atlantic. J. Clim. 22: 1469-1481.
Tsikliras, A.C. 2008. Climate-related geographic shift and sudden population increase
of a small pelagic fish (Sardinella aurita) in the eastern Mediterranean Sea. Mar. Biol.
Res. 4: 477-481.
ICES WGSPEC REPORT 2012
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Table 1. Metadata table indicating the small pelagics time series that have been investigated during the 2012 meeting of the WGSPEC.
Sardinella aurita
Start
Finish
NW Africa_Morocco
Maria Teresa Garcia & Eva Garcia-Isarch
Maria Teresa Garcia & Eva Garcia-Isarch
Mauritania_NW Africa
Maria Teresa Garcia & Eva Garcia-Isarch
Senegal_NW Africa
NW Mediterranean_Spain
Isabel Palomera
SW Mediterranean_Spain
Alberto Garcia & Ana Giraldez
Eastern Mediterranean_Greece
Athanasios Tsikliras
Northern Adriatic_Chioggia
Alberto Barausse-Carlotta Mazzoldi
Eastern Mediterranean_Israel
Egypt*
Palestine*
Syria*
Contact person
1990
1990
1970
1945
1945
1928
1997
1970
1970
1996
1976
2010
2010
2010
2010
2010
2009
2011
2008
2008
2008
2008
Engraulis encrasicolus
Contact person
Start
Finish
Steve Coombs
ICES (Unai Cotano)
ICES (Miguel Santos)
ICES (Fernando Ramos)
Eva García-Isarch
Eva García-Isarch
Isabel Palomera
Ana Giraldez
Piera Carpi & Alberto Santojanni
Alberto Santojanni
Alberto Santojanni
Alberto Barausse-Carlotta Mazzoldi
Andrea DeFelice
Andrea DeFelice
Athanasios Tsikliras
1910
1940
1943
1989
1970
1988
1940
1945
1975
1975
1975
1945
1976
1987
1928
1970
2010
2010
2010
2010
2010
2010
2010
2010
2010
2010
2010
2011
2010
2010
2009
2009
Contact person
Start
Finish
Steve Coombs
ICES (Unai Cotano)
ICES (Miguel Santos)
ICES (Fernando Ramos)
ICES (Miguel Santos)
1910
1940
1940
1907
1927
2010
2010
2009
1997
1988
ICES (Miguel Santos)
Maria Teresa Garcia & Eva García-Isarch
Maria Teresa Garcia & Eva García-Isarch
Maria Teresa Garcia & Eva García-Isarch
Maria Teresa Garcia & Eva García-Isarch
Isabel Palomera
Ana
Piera Carpi & Alberto Santojanni
Alberto Santojanni
Alberto Santojanni
Alberto Barausse-Carlotta Mazzoldi
Andrea DeFelice
Andrea DeFelice
Athanasios Tsikliras
1940
1976
1976
1995
1990
1945
1945
1975
1975
1975
1945
1976
1987
1928
2009
2010
1999
2010
2010
2010
2010
2010
2010
2010
2011
2010
2010
2009
Contact person
Start
Finish
Aril Slotte
1907
2010
English Channel_
Bay of Biscay(VIIIc)_Spain
Portugal_Miguel (IXa_S_Portuga
Spain_Miguel (IXa_S_Spain)
NW Africa_Morocco
NW Africa_Morocco
NW Mediterranean_Spain
SW Mediterranean_Spain
Adriatic Sea_Italian coast
Adriatic Sea_Croatian coast
Adriatic Sea_Slovenian coast
Northern_Adriatic_Chioggia
NW_Adriatic
SW_Adriatic
Greece
Turkey
Sardina pilchardus
English Channel_
Bay of Biscay(VIIIc)_Spain
IXa_South_Portugal
IXa_North_Spain
IXa_Central_North_Portugal
IXa_Central_South_Portugal
NW Africa_Morocco
NW Africa_Morocco
Mauritania_NW Africa
Senegal_NW Africa
NW Mediterranean_Spain
SW Mediterranean_Spain
Adriatic Sea_Italian coast
Adriatic Sea_Croatian coast
Adriatic Sea_Slovenian coast
Northern_Adriatic_Chioggia
NW_Adriatic
SW_Adriatic
Greece
Clupea harengus
Norvegian Sea_spring
Gaps
Frequency
Data
Source
yearly
landings
CECAF
yearly
landings
CECAF
yearly
landings
CECAF
yearly, monthly since 1940
landings
CSIC
yearly, but also monthly
landings
IEO
Aristotele
1949-1970 yearly, monthly since 1982andings, CPUE since 1982
University of Padova
yearly, monthly
landings
yearly
landings
GFCM
yearly
landings
GFCM
yearly
landings
GFCM
yearly
landings
GFCM
Gaps
Frequency
Data
Source
Comments
* Sardinella spp.
* Sardinella spp.
* Sardinella spp.
Comments
monthly
eggs
MBA
yearly
landings
ICES
yearly
landings
IPIMAR, ICES
yearly
landings
IEO, ICES
yearly
landings
CECAF
Includes IEO data
2000-2006
yearly, monthly
landings, CPUE
IEO
Only Spanish Fishery - IEO
yearly, monthly since 1940
landings
CSIC
yearly, but also monthly
landings
IEO
yearly
landings
CNR-ISMAR
yearly
landings
Split IOF
It includes data from Slovenia til 1998
yearly
landings
Lubjana FRIS
It includes data from Croatia til 1998
University of Padova
yearly, monthly
landings
some gaps
yearly
acoustic survey
CNR-ISMAR
some gaps
yearly
acoustic survey
CNR-ISMAR
yearly, monthly since 1964?andings, CPUE since 1982
Aristotele
yearly
landings
GFCM
Gaps
1915-1921
Frequency
Data
Source
Comments
monthly
yearly
yearly
yearly
yearly
eggs and larvae?
landings
landings
landings
landings
MBA
ICES
IPIMAR, ICES
IEO, ICES
IPIMAR*
eggs and larvae
Frequency
Data
Source
Comments
Yearly
Landings, SSB, R0
Data from 1 harbour only till 1940.
*Data provided by Rafael González-Quirós
yearly
landings
IPIMAR, ICES
yearly
landings
CECAF
Includes IEO data
yearly, monthly
landings, CPUE
IEO
Only Spanish Fishery - IEO
yearly
landings
CECAF
yearly
landings
CECAF
yearly, monthly since 1940
"
CSIC
yearly, monthly
landings
IEO
yearly
landings
CNR-ISMAR
yearly
landings
Split IOF
It includes data from Slovenia til 1998
yearly
landings
Lubjana FRIS
It includes data from Croatia til 1998
University of Padova
yearly, monthly
landings
some gaps
yearly
acoustic survey
CNR-ISMAR
some gaps
yearly
acoustic survey
CNR-ISMAR
yearly, monthly since 1964andings, CPUE since 1982
Aristotele
Gaps
3
Case studies
3.1
Long Term Variability of the Canary Current Upwelling System
Toresen and Østvedt 2000, ICES 2011
P. Relvas, J. Luís, P. Laginha Silva and A. M. P. Santos
There is almost total consent that a global warming of the upper ocean is occurring.
Accordingly, our analysis from several data sets (ICOADS, Portuguese Met. Office,
satellite imagery) show a consistent warming of the coastal and offshore upper waters of the Canary Current Upwelling System (CCUS), defined from 10ºN (Senegal
coast) to 43ºN (northern Iberian Peninsula). It includes a region south of Cape Blanc
(21º N) were the upwelling is seasonal during winter, a central region of NW Africa
(21–33º N) where upwelling is permanent and strong, and a northern sector that corresponds to the Iberian Peninsula (37–43ºN), where upwelling is seasonal during the
summer. It includes also the discontinuity imposed by the entrance of the Mediterranean/Gulf of Cadiz.
Until the systematic observation of the ocean through satellites, the ocean circulation
was viewed as consisting primarily of a large-scale slowly changing flow. However,
the present view of the upwelling systems points to an extremely noisy ocean circulation, where the meso-scale activity obscures the large-scale climatologic patterns and
largely governs the ecosystem functioning. A succession of jets, meanders, eddies,
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ICES WGSPEC REPORT 2012
upwelling filaments, coastal counter-currents and buoyant plumes that represent the
“weather” of the ocean, superimposes on the larger scale circulation distorting the
classical view of the ocean circulation. This meso-scale activity is a fundamental scale
for the marine ecosystem behaviour, because the spatial and temporal scales of importance for marine plankton communities are mainly related to meso-scale features.
The question is: How does the CCUS respond to the global scale warming?
To answer this question we made use of the satellite SST imagery (AVHRR Pathfinder SST Version 5.1 –quality 6 and 7 only), the most suitable data for the mesoscale analysis due to their good time-space resolution and continuous coverage. A
considerable amount of years of continuous satellite remote sensing SST measurements is already available and long enough to attempt the analysis of long-term
changes (1982–2009). A hierarchical suite of tests and procedures were applied to the
imagery data to guarantee their quality and that the annual and seasonal averages are
not biased towards the seasonally more abundant summer temperature data. A robust linear fit was then applied to each individual pixel, crossing along the time the
same 4x4 km pixel in all the processed monthly mean AVHRR SST images from 1982
until 2008. The slope of the linear fit would represent the temporal variation of the
SST. A warming field was created upon the slopes of the linear fits applied to each
pixel, in a way that the value associated to each pixel represents the SST trend from
1982 to 2009 in ºC/year. The global synthesized image is shown below in the figure,
along with enlargements of specific regions.
ICES WGSPEC REPORT 2012
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Figure A. Warming trends in the period 1982–2009. Entire CCUS region (left) and details of mesoscale features (right).
The computed field of SST trends exhibits regions with clear contrasting warming
trends. The global warming affects the coastal ocean of the CCUS as a whole, but the
response is not spatially uniform. Different meso-scale features respond to the rise of
the temperature in different ways. If we assume that the SST contrast between coastal
and offshore waters is a proxy for the upwelling intensity, the presented results point
to an intensification of the meso-scale activity of the CCUS, with the intensification of
the SST gradients as a response to the observed warming.
The spatial heterogeneities are an indication of the main role that meso-scale processes play in the modulation of the spatial and temporal variability of SST, namely at
the decadal scale.
Specifically:
•
•
•
Decrease of upwelling intensity in the southern part of the CCUS, between
Cape Blanc and Cape Verde.
Re-inforcement of the coastal upwelling structures off NW Africa: Dakhla
upwelling center (from 22ºN to 28ºN) and Cape Ghir (31ºN) upwelling
filament evidences an intensification of the upwelling intensity.
Upwelling intensification off the southern part of the Iberian Peninsula,
contrasting with a more regular behaviour further north.
We can conclude that in Eastern Boundary Upwelling Systems, where meso-scale
structures play a major role in the description of the upwelling regime, to rely on
sparse spatial observations to hypothesize about the decadal behaviour of the upwelling intensity at the basin scale may be questionable.
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3.2
ICES WGSPEC REPORT 2012
NAO related small pelagic fisheries fluctuations off Morocco and Senegal
L. Fernández-Peralta, C. Meiners1, M.T. García Santamaría, B. Samb2
1
Universidad Veracruzana (Veracruz), Mexico, 2Centre de Recherches Océanographiques (Dakar),
Senegal
Introduction
The small pelagics are one of the most important fish resources off the North West
African coast. These resources are shared between different countries and are exploited by artisanal and industrial fleets.
Cupleids as Sardina pilchardus and Sardinella spp (S. aurita and S. maderensis) are important target species and make up over 80% of small pelagic catches in Morocco and
Senegal. The fishing activity in this area and their statistics provide us ecological time
series, which are suitable to compare with the dynamics of the climatic system.
Hydroclimatic regime
The large-scale small pelagic fisheries are supported by an important productive marine region in the NW African region: The Canary Current ecosystem, which is one of
the largest wind-induced upwelling systems.
The seasonality of the upwelling and the displacement of a marine front along the
coast of Mauritania and Senegal cause a “contrasting hydroclimatic situations” with
cold waters in winter, warm waters in summer and two short transition periods between both seasons. This area is an important transition zone, both hydrologic and
faunistic, between an “equatorial” warm region and a “Canary” cold region. (Wooster and McLain, 1976; Belvèze and Erzini, 1983).
This large abundance of small pelagics means that there is an important intermediate
trophic level in this large ecosystem. Despite their importance, little is known about
the climate effects in the region.
NAO Index (Why use NAO?)
The NAO is the most robust pattern of recurrent atmospheric behaviour in the North
Atlantic region (Hurrell and Dickson, 2003). NAO fluctuations are widest during the
colder months (December–March) when the atmosphere is most active dynamically
(Hurrell et al., 2003; Stenseth et al., 2003).
The NAO index reduces complexity of time-space variability into simple measures,
representing a “weather package”, and might provide an assessment of the ecological
effects of climate fluctuations.
Most research about the NAO and its effects has been made in the North Atlantic,
where this climatic proxy explains a great part of the climate variability., The research
on the relationship between climate processes and the Northwest African upwelling
system began only a few years ago.
The NAO effects in NW Africa produces during the positive phases (NAO+) an intensification of the trade winds from the northeast and, as a consequence, an increase
of the upwelling and cooling water. An inverse situation occurs during the negative
phases (NAO-). The fluctuations in the upwelling extension are controlled by the
predominant winds that are initiated in the Subtropical Atlantic, the trade winds,
which are largely determined by the NAO (Van Camp et al., 1991; Nykjaer and Van
Camp, 1994). The NAO explains 50% of SST annual variability in the open sea in this
Atlantic area (Helmke, 2003). The wind stress north-south component ( y) of the
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wind vector correlates significantly with the winter NAO index in most of the Atlantic basin (Visbeck et al., 1998)
Background in Morocco and Senegal
Wind stress
In the NW Africa, NAO explained a high percentage of the variability of the winds in
Morocco, off 21ºN (Meiners, 2007). The wind stress component ( y) was in synchrony
and positively correlated with the NAO index. This proxy explained around 41% of
wind stress variability in this wide area.
The same results were obtained in Mauritania and Senegal waters (from 21ºN to
15ºN) where the wind stress component ( y), showed changes in accordance with opposite NAO phases during the period 1960–2004 (Meiners et al., 2010). The Figure 1
shows the high synchrony between NAO index and wind stress v-component ( y)
time-series at time t, and were positively and significantly correlated (r=0.72; F1,
43=48.3265, p<<0.001). NAO explained around 53% of wind stress variability in this
southern area.
Figure 1. Synchrony between NAO index and wind stress v-component time-series at time t. Note
that the negative sign indicates north–south vector (from Meiners et al., 2010).
Upwelling
The NAO explains a high percentage of the upwelling variability periods to around
21ºN, and its changes were in phase and positively related with NAO fluctuations
(Meiners, 2007).
A relation between the upwelling extension and intensity with the wind stress was
observed in Mauritanian and Senegalese waters with high local variability. In the
NAO-negative phases (1960–1973) the conditions for intense upwelling were less extended than during NAO-positive phases (1990–2000); (Meiners et al., 2010).
Primary production
In this area, the high concentrations of photosynthetic pigments imply a significant
productivity (Freudenthal et al., 2001), due to the sustained supply of nutrients, the
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ICES WGSPEC REPORT 2012
upwelling, and its retention or recirculation in the surface waters by the meso-scale
processes.
Meiners (2007) find a strong and proportional relation at the same time t between
wind stress, NAO and primary production with the chlorophyll concentrations from
satellite imagery in Moroccan waters.
Objective
Recent studies in NW Africa waters have shown that wind-induced upwelling (τy)
and primary production are related with the NAO. A significant relationship between hake abundance and the NAO index was observed (Meiners, 2007; Meiners et
al., 2010). Moreover, the hake is an important predator of clupeids and its abundances
might be related.
Considering this, the goal of this approach was to perform an explorative analysis to
test the possible relationship between the climate variability described by the NAO
index and the abundance of small pelagics in Morocco and Senegal.
Methods
Fishery data
Annual CPUE data as abundance proxies from three commercial small pelagic species:
•
•
•
Sardinella aurita: between 1981–2005 (25 years), from the artisanal fleet in
Senegal. The catch is in tonnes and the effort in fishing trips.
Sardinella maderensis: between 1990–2005 (16 years), from the artisanal fleet
in Senegal. The catch is in tonnes and the effort in fishing trip.
Sardina pilchardus: between 1990–1999 (10 years) from the industrial Spanish purse seiners fleet, fishing south to 26°N, in Saharan waters. The catch
is in tonnes and effort in fishing days.
NAO index
The winter NAO index, between December to March. Source: National Center for
Atmospheric Research (NCAR) http://www.cgd.ucar.edu/cas/jhurrell/indices.html.
(Hurrell, 1995). NAO data were smoothed by a running average of 3 years to reduce
time-series noise.
Analysis
Correlation techniques were used to analyze and quantify the relationships between
climate variability (NAO index) and the annual yields of the small pelagic species at
the same time. The statistical significance of each relation was estimated by an
ANOVA (F test).
Results
A quadratic dependence between abundance series of small pelagic species and the
NAO index of the same year (t) was found in all cases.
Sardinella aurita
There was a synchrony between the residuals of the CPUE and the smoothed NAO.
The highest CPUE values coincided with the largest positive anomalies of the NAO,
and negative residuals corresponded to negative NAO values.
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A negative quadratic dependence was obtained and the polynomial regression was
statistically significant (p<0.05) between the residuals CPUE and the NAO index. The
proxy explains around 32% of abundance variability of this species (Figure 2).
Re sid u a ls CPUE ( t / t rip )
2
1
0
R 2 = 0 .3 2 1 1
r = 0 .5 7
p< 0 .0 5
-1
-2
-2
-1
0
1
2
3
4
N AO I nde x ( t )
Figure 2. Negative polynomial relationship between residuals CPUE of S. aurita and NAO index
at the same t.
Sardinella maderensis
A positive quadratic function was obtained, statistically significant (p<0.05), between
the CPUE time series and the climatic proxy. In this case, the NAO explains around
42% of abundance variability of this species (Figure 3).
0 ,3
Log CPUE ( t / t rip )
0 ,2
0 ,1
0
- 0 ,1
2
R = 0 ,4 2 1 6
r = 0 .6 5
p< 0 .0 5
- 0 ,2
- 0 ,3
-2
-1
0
1
2
3
4
N AO I nde x ( t )
Figure 3. Positive polynomial relationship between residuals CPUE of S. maderensis and NAO
index at the same t.
Sardina pilchardus
This species provided a weak fit, but one must take into account that is a very short
time series (only 10 years).
The negative quadratic dependence obtained was not statistically significant (p>0.05).
The NAO explains only 14% of abundance variability of this species. The results were
not conclusive.
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ICES WGSPEC REPORT 2012
Discussion
The winter NAO index changes are supposed to have immediate effects on fast growing species such as small pelagics.
The quadratic responses may suggest an "environmental window" defined by the
NAO for every species, showing a mid-high dependence of the abundance with respect to the NAO index for Sardinella species.
S. aurita presented a broad “environmental window", with optimal NAO values in
the range from -1 to 0 and >2. S. maderensis showed an inverse relationship, with optimal NAO values between 0 and 1.7, given the fit to positive quadratic function.
S. pilchardus had the widest window (from -1.1 to 3.4) and a negative relationship
with the NAO, as S. aurita, although the results are not conclusive, surely because the
series is not long enough. However, this species has shown strong dependence with
oceanographic conditions in the North Atlantic (Guisande et al., 2001; Santos et al.,
2001), and one may assume that the response to the NAO index is close. Probably, a
relationship would be indicated by a longer time series.
Contrasting reactions between Sardinellas species suggest important ecological differences in response to the same phenomena and a less competitive behavior of S. maderensis. In fact, this species is less abundant in the catches and its distribution is more
restricted than that of S. aurita. In addition, the broad “environmental window” of
this latter species could imply greater abundances and a wider latitudinal distribution when compared with S. maderensis, at it really occurs.
One may also deduce from these results that S. maderensis is a more “tropical” and S.
aurita more “temperate” species.
The similar behaviour of S. aurita and S. pilchardus, another “temperate” species,
could point to a comparable ecological role on both sides of the permanent upwelling, but the results are inconclusive with respect to the of sardine.
In general terms, it is necessary to use longer time series in order to establish conclusions about relationships with large-scale phenomena such as the NAO index and, in
these cases, further analysis is required.
In any case, to describe and quantify these relationships it is helpful to consider climate factors as state variables in predictive and functional fishery models. Also, different kinds of relationships may explain diverse features in ecological terms,
showing divergent effects over species under fishing pressure in the same region.
References
Belvèze H. & Erzini, K. 1983. The influence of hydroclimatic factors on the availability of the
sardine (Sardina pilchardus, Walbaum) in the Moroccan Atlantic fishery. In: G. D. Sharp &
J.Csirke (Eds.). Proceedings of the expert consultation to examine changes in abundance
and species composition of neritic fish resources, 285-327. FAO, Rome.
Freudenthal, T., Meggers, H., Henderiks, J., Kuhlmann, H., Moreno, A., Wefer, G. 2002. Upwelling intensity and filament activity off Morocco during the last 250 000 years. Deep Sea
Research II 49, 3655-3674.
Guisande C., Cabañas J. M., Vergara A. R., Riveiro I. 2001. Effect of climate on recruitment success of Atlantic Iberian sardine Sardina pilchardus. Marine Ecology Progress Series 223,
243-250.
Helmke, P. 2003. Remote sensing of the Northwest African upwelling and its production dynamics. Tesis doctoral. Universität Bremen, Alemania. 165 pp.
ICES WGSPEC REPORT 2012
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Hurrell, W., 1995. Decadal trend in the North Atlantic Oscillation: regional temperatures and
precipitation. Science 269, 676–679.
Hurrell, W., Dickson, R., 2003. Climate variability over the North Atlantic. In: Hurrell, J.,
Kushnir, Y., Ottersen, M., Visbeck, M. (Eds.), The North Atlantic Oscillation: Climatic Significance and Environmental Impact. American Geophysical Union, pp. 15–31.
Hurrell, W., Kushnir, Y., Ottersen, G., Visbeck, M. 2003. An overview of the North Atlantic
Oscilation. En: J. Hurrell, Y. Kushnir, G. Ottersen, M. Visbeck (Eds.) The North Atlantic
Oscillation: climatic significance and environmental impact 1-35 pp. American Geophysycal Union.
Meiners, C. 2007. Importancia de la variabilidad climática en las pesquerías y biología de la
merluza europea (Merlucccius merluccius L.) de la costa Noroccidental Africana. Ph.D thesis. Universitat Politècnica de Catalunya. 206 pp.
Meiners, C., Fernández, L., Salmerón, F., Ramos, A. 2010. Climate variability and fisheries of
black hakes (M. polli and M. senegalensis) in NW Africa: A first approach. Journal of Marine
System, 80, 243-247.
Nykjaer, L., Van Camp, L., 1994. Seasonal and interannual variability of coastal upwelling
along northwest Africa and Portugal from 1981 to 1991. J. Geophys. Res. 99, 14197–14207.
Santos, A.M.P., Borges, M.F., Groom, S. 2001. Sardine and horse mackerel recruitment and upwelling off Portugal. ICES Journal of Marine Science 58, 589-596
Stenseth, N., Ottersen, G., Hurrell, W., Mysterud, A., Lima, M., Chan, K., Yoccoz, N., Ådlandsvik, B., 2003. Studying climate effects on ecology through the use of climate indices: the
North Atlantic Oscillation, El Niño Southern Oscillation and beyond. Proc. R. Soc. Lond.
270, 1–10.
Van Camp, L., Nykjaer, L., Mittelstaedt, E., Schlittenhardt, P., 1991. Upwelling and boundary
circulation off northwest Africa as depicted by infrared and visible satellite observations.
Prog. Oceanogr. 26, 357–402.
Visbeck, M., Cullen, H., Krahmann, G., Naik, N.H. 1998. An ocean models response to North
Atlantic Oscillation-like wind forcing. Geophysical Research Letters, 25, 4521-4524.
Wooster, W.S. & McLain, D.R. 1976. The seasonal upwelling cycle along the eastern boundary
of the North Atlantic. Journal of Marine Research 34, 131-140.
3.3
Historical landings of small pelagics off North West Africa. “Signals” of the
climatic effect on small pelagics in North West Africa and in the Canaries
M.T. García Santamaría, E. García-Isarch
Introduction
The North West African marine area located between 36ºN and 12ºN belongs to the
Canary Current Large Marine Ecosystem, which is one of the most productive areas
in the world. The high productivity of this ecosystem supports very important fishery
resources that have led to a great development of the fishing activity in the area. West
African stocks are exploited by the coastal countries as well as by foreign fleets. This
fact advises the establishment of a scientific cooperation framework, over-arching
cooperative actions, such as the assessment of the exploited resources. This scientific
framework is provided by the Committee for the Eastern Central Atlantic Fishery
(CECAF) and NW African stocks are assessed in the CECAF Working Groups (Subgroup North).
Three main data sources have been analysed to study the temporal evolution of small
pelagics in North West Africa:
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ICES WGSPEC REPORT 2012
a ) FishStat Plus-universal software for fishery statistical time series, compiled
by the Food and Agriculture Organization (FAO). This provides only catch
data.
b ) Data compiled by the CECAF Working Groups of Small Pelagics (Subgroups North). These are catch data and effort data (not in all cases).
c ) Spanish fishery data in Morocco. This source should be considered due to
the higher disaggregation level in relation to the two above-mentioned. It
corresponds to the anchovy and sardine data series of the Spanish fisheries
developed in Moroccan waters which is managed by different fishing
agreements since 1979. The control and monitoring of this fishery information is carried out by the Instituto Español de Oceanografía (IEO).
Temporal evolution of small pelagic catches in NW Africa
Figure 1 shows the catch trends of small and medium sized pelagic species in the last
20 years (1990–2010) in North West Africa, from Morocco to Senegal (both countries
included).
1200000
1000000
S. pilchardus
Catch (t)
800000
600000
S.aurita
S.maderensis
E.encrasicolus
400000
200000
T. trachurus
T. trecae
S.colias
0
Figure 1. Catch trends of small and medium sized pelagic species in North West Africa. Period
1990–2010. Source: CECAF Small Pelagics Working Group, Subgroup North (FAO 2011, in press).
Sardine (Sardina pilchardus) comprises the highest catches during the whole period,
followed by round sardinella (Sardinella aurita). It is worth mentioning the opposite
catch trends of both species during this period. Sardine catches were maximal at the
beginning of the nineties, when S. aurita was caught at very low levels. However,
sardine showed a general decreasing trend in this decade, while sardinella increased
to reach a very high level in 1998. The trends were opposite in the following years,
with a sardine general increase in the period 1999–2005 and sardinella decrease in
1998–2004. Sardinella catches generally increased in the last years of the series, while
sardine trends were more variable (decrease in 2005–2007, increased in 2007–2009
and new decrease in 2010).
Together with this opposite temporal catch trends, changes in the distribution patterns of sardine and round sardinella occurred in NW Africa during the last 20 years,
with general displacement processes of both species (S. pilchardus towards the South,
and S. aurita towards the North). In this sense, first records of sardine in Senegalese
waters were reported at the end of the eighties, with maximal catches in the period
2004–2008. In the same period a general increase of S. aurita catches has been registered in Morocco.
ICES WGSPEC REPORT 2012
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Previous studies of climatic influence on small pelagics off NW Africa
There are several studies on the influence of climatic or other environmental conditions on fisheries and spatial and temporal reproduction/recruitment strategies of
small pelagics in NW Africa. However, our research effort has not been concretely
directed to this topic although we have developed several studies and observed certain evidences on the climatic/environmental effect on small pelagics that can be considered occasional and spread in time. Some examples are explained below:
•
•
•
The
analysis
of
the
relationship
between
satellite-derived
(AVHRR/NOAA-11) SST and the location of sardine fishing grounds of the
Spanish purse seiner fleet in the NW African upwelling showed a SST
range of 17.6°C–21.1°C in the sardine fishing grounds, while the SST corresponding to the maximal sardine yields was between 19.93°C–21.13°C
(Ramos and Santamaría, 1998).
The analysis of the relationship between SST and the catches of sardine
and round sardinella in Mauritania in the period 2004–2007 showed a general decrease of sardine together with a progressive increase of S. aurita
(Pascual-Alayón et al., 2008a). This clear seasonal variability in landings
was coincident with both species spawning seasons (winter for sardine
and early summer for sardinella).
The analysis of the relationship between SST and the evolution of the Gonadosomatic Index (GSI) of S. aurita off Mauritania revealed the onset of
the maturation process occurring during the SST rising periods, while the
GSI decreased during the warmest months (Pascual-Alayón et al., 2008b).
Signals of the climatic influence on Small Pelagics off the Canary Islands
In the same way as in NW Africa, we have found certain signals that may reflect a
climatic/environmental effect on the small pelagics off the Canary Islands. These are
summarized as follow:
•
•
•
The relationship between monthly satellite–derived SST and SST anomalies (SSTA) and a catch index (CI) of small and medium sized pelagic species (sardine S. pilchardus, round sardinella S. aurita, flat sardinella S.
maderensis, anchovy E. encrasicolus, chub mackerel Scomber colias and horse
mackerel Trachurus picturatus) in Gran Canaria was analyzed. Results
showed that the CI increased with a lag in relation to a cooling process
during the previous months and that , in turn, the CI decreased after the
warming processes (López-Abellán et al., 2008). However, it is worth reminding that only two years were analysed and therefore these results
should be considered with caution.
Mean monthly lengths of T. picturatus sampled from Tenerife catches during the period from March 2005 to March 2006 were analysed in relation to
monthly SSTs and SSTAs. Results showed that the species recruitment,
considered as the period with the smaller mean lengths, occurred during
the season with the maximal SST values and certain stabilization of SSTA
(Jurado-Ruzafa and Santamaría, 2011).
The spawning of S. pilchardus and S. colias was analysed in relation to SST,
from Tenerife catches during the period March 2005 – March 2006. The
GSIs of both species increased in the first quarter of the year coinciding
with the period with the lowest SST values (about 19ºC).In contrast, GSIs
were minimal during the warmest period. However, the qualitative analy-
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ICES WGSPEC REPORT 2012
•
•
•
sis showed that the GSI increases do not correspond to a spawning peak
but to a post-spawning stage (Santamaría et al., 2008a). Although there are
no studies about this, we wonder if this low spawning intensity could be
related to a genetic migration process.
A gradual replacement of sardine by round sardinella has been detected in
the Canaries. Traditionally, sardine has been the second most important
small pelagic species caught in the Canary Islands while round sardinella
was an additional species without much importance. However, during the
nineties, this situation changed and round sardinellas were more abundant
than sardines during many years (Santamaría et al., 2008b). An important
temperature rise was registered in the Canaries in 1995, with a maximum
SST occurring in 1997. The warming of the sea water during this period
may have favoured S. aurita and affected negatively S. pilchardus. However, last catch data from 2010/2011 revealed a new increase of sardine
catches, reaching similar levels as round sardinella.
The case of the anchovy off the Canary Islands in 1999: Anchovy catches
traditionally had occurred off the eastern Canary Islands (Lanzarote,
Fuerteventura and Gran Canaria). However, in 1999 large amounts of anchovy were caught off the western islands (Tenerife, La Gomera, La Palma
and El Hierro). Satellite images showed unusual North-East trade winds
during April and May 1999, that derived as an expansion of the African
upwelling influence at the Canaries, at distances up to 450 km (El Hierro
Island). This was reflected in the transport of cold and turbid waters (due
to the high chlorophyll concentrations) to the traditionally oligotrophic insular ecosystems (Ramos, pers. comm.). The high anchovy catches offthe
western islands could be attributed either to an exceptional recruitment
due to better environmental conditions that favoured early life stages survival or to an exceptional larval transport from the African coastal waters
to the Canary Islands. Currently, anchovy catches mainly occur (never in
high amounts) off the eastern islands and are not very frequent off the
western islands.
An establishment of species of the Genus Decapterus has been observed off
the Canary Islands. Decapterus macarellus and D. punctatus had been considered as rare species with sporadic presence off the western islands of
the Canaries until the beginning of the 2000s. However, from 2007 onwards these species have been more or less continuously caught off a
western island (La Palma) as well as off the central islands (Tenerife and
Gran Canaria). This fact has been coincident with the SST and SSTA increases occurring during the same period that could have favoured the
displacement and establishment of warmer species with high mobility
such as these Decapterus spp (González-Lorenzo et al., 2011). On the other
hand, there is a longitudinal gradient of temperature in the Canaries Islands in a way that the western islands are warmer than the others. This
warmer and more oceanic character of the western islands could explain
the higher presence of D. macarellus and D. punctatus ioff La Palma and El
Hierro. The appearance and establishment of these species with southerly
distributions off the Canaries lead us to suspect that a “tropicalization”
phenomenon may be occurring in the area.
ICES WGSPEC REPORT 2012
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References
FAO, 2011. Tenth meeting of the FAO Working Group on the Assessment of Small Pelagic Fish
off Northwest Africa. Banjul (Gambia), 18-22 May 2010.
González-Lorenzo, J.G., M.T.G. Santamaría, P. Martín-Sosa, J.F. González and S. Cansado,
2011. Establecimiento de las especies del género Decapterus en las Islas Canarias. XVI Symposium Ibérico de Estudios de Biología Marina, Alicante (España).
Jurado-Ruzafa, A. and M.T.G. Santamaría, 2011. Notes on the recruitment of the blue jack
mackerel Trachurus picturatus (Bowdich, 1825) off the Canary Islands (Carangidae, Perciformes). Vieraea 39: 219-224.
López Abellán, L.J., M.T.G. Santamaría, J.F. González, A. Barrera, E. Balguerías and M.E.
Quintero, 2008. The incidence of SST and SSTA on the Small Pelagics catches from the Canary Islands. Science and the Challenge of Managing Small Pelagic Fisheries on Shared
Stocks in Northwest Africa. 11–14 March 2008 Casablanca, Morocco.
Pascual-Alayón, P., M.T.G. Santamaría, E. Balguerías, E. Hernández, L. Bravo de Laguna, A.
Sancho and V. Duque. 2008a. Activity of European pelagic trawlers fishing in Mauritania
and landing in the port of Las Palmas de Gran Canaria (Canary Islands, Spain) from 2004
to 2007. Relationship between catches and SST / SSTA. Science and the Challenge of Managing Small Pelagic Fisheries on Shared Stocks in Northwest Africa. 11–14 March 2008
Casablanca, Morocco.
Pascual-Alayón, P., A. Sancho, E. Hernández, M.T.G. Santamaría, V. Duque, E. Balguerías, L.
Bravo de Laguna, C. López and C. Presas, 2008b. Reproductive aspects of sardine, round
Sardinella, flat Sardinella and mackerel off Mauritanian waters (NW Africa). Science and
the Challenge of Managing Small Pelagic Fisheries on Shared Stocks in Northwest Africa.
11–14 March 2008 Casablanca, Morocco.
Ramos, A.G. y M.T.G. Santamaría, 1998. Aplicación de la teledetección espacial infrarroja a la
pesquería española de sardina (Sardina pilchardus Walbaum, 1792) en áreas del afloramiento noroccidental africano. Informe Técnico del Instituto Español de Oceanografía
nº 172: 34 pp.
Santamaría, M.T.G., J.F. González, M.E. Quintero, L.J. López Abellán, A. Barrera, E. Balguerías,
J.A. Díaz Cordero, C. López, C. Presas and V. Duque. 2008a. Maturity and Spawning of
some Small Pelagic Fishes in the Canary Islands related to SST conditions. Eastern Boundary Upwelling Ecosystems. Integrative and Comparative Approaches. Las Palmas de Gran
Canaria (España), 2-6 June 2008.
Santamaría, M.T.G., J.F. González, A. Barrera, L.J. López Abellán, M.E. Quintero and E. Balguerías. 2008b. Substitution of sardine (Sardina pilchardus) for Round Sardinella (Sardinella
aurita) in the Canary Islands waters. Eastern Boundary Upwelling Ecosystems. Integrative
and Comparative Approaches. Las Palmas de Gran Canaria (España), 2-6 June 2008.
3.4
Decadal changes in sardines and anchovies in the Canary Current
Upwelling System
A.M. P. Santos
The Canary Current Upwelling System (CCUS) covers the latitudinal range 12–43º N
and has some particularities in relation to the other three major Eastern Boundary
Upwelling Systems (EBUS), namely a major interruption in the continuity of the system at the Strait of Gibraltar and that it is the only one with a sardine species from a
different genus (Sardina vs Sardinops). This poses, at least, two questions which have
still not been answered: Is there a continuity of the flow between the northern (Iberia)
and southern (NW Africa) part of the system? Why is there no alternation between
sardine and anchovy regimes as in other EBUS?
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ICES WGSPEC REPORT 2012
The bulk of the sardine population is located in the southern part of CCUS off NW
Africa. Important fluctuations in landings have been observed in the last 70 years but
they seem to be out of phase between the two sub-regions (Iberian vs. NW Africa).
The explanation for these fluctuations have been related, at least partially, to environmental drivers (e.g. Santos et al., 2001, 2004, 2005; Borges et al., 2003) but also to
changes in exploitation (e.g. Carrera & Porteiro, 2003).
The normalised and detrended landing time series of sardine, anchovy and sardinella
in the CCUS are presented in Figure 3.4. These time series were used to perform an
exploratory analysis to investigate the relationships between small pelagic fish species in the CCUS and climatic indexes (the North Atlantic Oscillation (NAO) and the
East Atlantic (EA) pattern).
The most interesting results of the correlation analysis between these time series
showed:
1 ) Sardine and anchovy off NW Africa are positively correlated;
2 ) Sardine in ICES Div. IXa is negatively correlated to sardinella off NW Africa;
3 ) Sardine off NW Africa is negatively correlated to sardine in ICES Div. IXa.
However, the correlation is not statistically significant at p < 0.05 (only at p
< 0.15);
4 ) Sardine and anchovy in CCUS are, in general, correlated to the EA pattern,
negatively in the case of sardine in ICES Div. IXa, and positively in the
case of NW Africa sardine and anchovy in the whole CCUS;
5 ) Sardinella is only correlated to the NAO winter index.
The EA pattern positive phase is associated with above average temperatures and
below average precipitation in these southern regions. This could, at least partially,
explain:
1 ) The negative correlation of the EA pattern (January) with sardines in ICES
Div. IXa, considering that buoyant plumes seem to be important features
for the survival of sardine larvae in the spawning grounds off Western
Iberia (e.g. Santos et al., 2004).
2 ) The positive correlation with anchovies, considering that spawning in the
region is triggered by an increase of sea surface temperatures. However, it
does not explain the association between anchovy and rivers outflow.
References
Borges, M. F., Santos, A. M. P., Crato, N., Mendes, H., & Mota, B. (2003). Sardine regime shifts
off Portugal: a time series analysis of catches and wind conditions. Scientia Marina,
67(Supplement 1), 235-244.
Carrera, P., & Porteiro, C. (2003). Stock dynamics of the iberian sardine (Sardina pilchardus,
W.) and its implication on the fishery off Galicia (NW Spain). Scientia Marina, 67 (Supplement 1), 245-258.
Santos, A.M.P., Borges, M.F., & Groom, S. (2001). Sardine and horse mackerel recruitment and
upwelling off Portugal. ICES Journal of Marine Science, 58, 589-596.
Santos, A.M.P., Peliz, A., Dubert, J., Oliveira, P.B., Angelico, M.M., & Ré, P. (2004). Impact of a
winter upwelling event on the distribution and transport of sardine eggs and larvae off
western Iberia: a retention mechanism. Continental Shelf Research, 24, 149-165.
ICES WGSPEC REPORT 2012
| 19
Santos, A.M.P., Kazmin, A.S., & Peliz, A. (2005). Decadal changes in the Canary upwelling system as revealed by satellite observations: Their impact on productivity. Journal of Marine
Research, 63, 359–379.
Figure 3.4. Normalised and detrended time-series of landings in the CCUS for sardine, anchovy
and sardinella. Superimposed (black lines) are the climate indexes that showed the best correlations with the landing data (EAj5 is the 5-yrs running mean of the January East Atlantic (EA) pattern; EA5 is the 5-yrs running mean of the annual EA; EAw is the EA in winter months; EAw5 the
5-yrs running mean of the previous; NAOw5 is the 5-yrs running mean of the North Atlantic
Oscillation winter index).
Data sources: Sardine and anchovy landing data from ICES WGSANSA; Sardine NW Africa landing data from Souad Kifani and FAO Working Group on the Assessment of Small Pelagic Fish off
Northwest Africa; Anchovy NW Africa landing data from FAO Capture Production Statistics;
Sardinella landing data from FAO Capture Production Statistics and FAO COPACE/PACE Series
91/58.
3.5
Overview of large and meso-scale oceanographic processes relevant to
the Gulf of Cádiz
F. Ramos, R. Sánchez, Mª Paz Jiménez
The Gulf of Cádiz (GoC, Figure 1) is placed in the northern area of the Canary Current Large Marine Ecosystem and shares many of the oceanographic characteristics
typical of the Eastern Boundary Upwelling Systems (EBUSs) in the mid-latitudes (e.g.
seasonal alternation of a regime of winds favourable to the coastal upwelling, a high
biological productivity associated to this process, a system of zonal fronts and currents, and a coastal transition zone with a set of mesoscale structures that deform the
fronts favouring the coast-open ocean exchange). Its main distinctive features are: the
rupture of the N-S orientation of the coastline typical of the EBUSs by an E-W orientated coastline, the influence of a northern branch of the Azores Current, the presence
of the Strait of Gibraltar with its Atlantic-Mediterranean water exchanges and mixing, and the seasonality, that produces alternate regimes in the surface waters and an
intense generation of mesoscale features, which modulate and are modulated by the
exchange in the Strait (see e.g., García-Lafuente & Ruiz, 2007; Sánchez et al., 2006).
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ICES WGSPEC REPORT 2012
Figure 1. Surface circulation in the GoC. CC Cell: cyclonic cell over the shoals in front of Cape
Trafalgar; GCCC Cell: Gulf of Cadiz Counter Current; Upw. Jet: Portuguese upwelling (after Folkard et al., 1997; Peliz and Fiuza, 1999; Relvas and Barton, 2002; Sánchez and Relvas, 2003; CriadoAldeanueva et al., 2006; García-Lafuente et al., 2006; Sánchez et al., 2006; Peliz et al., 2009).
Cape Santa María divides the GoC shelf in 2 sectors that support different oceanographic processes (forcings by mass and energy inputs and tidal processes) with the
consequence that the eastern shelf is warmer and more productive than the western
one, which is subject to a more permanent upwelling (Navarro & Ruiz, 2006; Prieto et
al., 2009). In this eastern sector, which is shallower and which has a lower intensity of
currents, the Guadalquivir estuary also plays a relevant role (by constant tidal mixing) in the control of the biological activity on the shelf. For these reasons, these shelf
waters of the NE GoC, mainly those ones in the inner shelf surrounding the Guadalquivir River mouth, offer a favourable environment for the development of anchovy eggs and larvae in spring-summer and have become the main GoC anchovy
spawning area (Baldó et al., 2006). The outer stretch of the Guadalquivir estuary is
used almost synchronously by anchovy post-larvae and juveniles as a nursery area.
Recruitment to the estuary occurs when water temperature and salinity are relatively
high, but turbidity and rainfall are relatively low. Some studies (Baldó & Drake, 2002;
Drake et al., 2007; Fernández-Delgado et al., 2007; González-Ortegón et al., 2010) point
out that, within this optimal window, the main factor regulating the nursery function
of the estuary is the food availability of key-prey species (copepods for post-larvae,
the mysid Mesopodopsis slabberi for juveniles).
However, persistent easterly bursts (preceded and followed by intervals with a lower
frequency of this wind) may generate significant modifications in the oceanographic
regime in the GoC (i.e. decrease of SST, oligotrophy, offshore advection of early
stages away from favourable conditions), which can influence markedly the reproductive success of the species. These detrimental conditions were evident during the
period 1990–1997 and they seemed to affect the development conditions of eggs and
larvae, which could have resulted in failed recruitments in those years as evidenced
by the severe drop of landings in 1995–1996 (Ruiz et al., 2006, 2009; Figure 2). According to the authors, this drop of landings resembled more the easterly signal than the
NAO index or precipitation. Conversely, the 1996 rain fall peak (and associated river
discharges) – clearly reflecting the dramatic change in the NAO index– may have
played a role in the recovery of 1997 anchovy landings.
ICES WGSPEC REPORT 2012
| 21
Figure 2. A) GoC anchovy landings (ICES Subdivision IXa South; black circles) and Barbate’s
single-purpose purse-seine fleet CPUE (white circles, in kg/fishing trip). Barbate is considered as
a reference fleet in the GoC anchovy harvesting. Landing data for 2000 is not included in the
graph as catches were not representative due to social conflicts in the fleet. Bars accumulate the
time when easterlies stronger than 30 km/h hit Cádiz over the period from March to September.
B) Circles and bars indicate North Atlantic Oscillation index and annual precipitation, respectively. Source: Ruiz et al. (2006).
The GoC anchovy population has also experienced a noticeable decreasing trend during the period 2008–2010 as a probable consequence of successive failures in the recruitment strength in those years (Figure 3; ICES, 2011). A man-induced alteration of
the nursery function of the Guadalquivir estuary, caused by episodes of highly persistent turbidity events (HPTE; González-Ortegón et al., 2010), during the anchovy
recruitment seasons in 2008, 2009 and 2010 could be one plausible explanation. Thus,
the control of the Guadalquivir River flow, from a dam 110 km upstream, has an immediate effect on the estuarine salinity gradient, displacing it either seaward (reduction) or upstream (enlargement of the estuarine area used as nursery). This also
affects the input of nutrients to the estuary and adjacent coastal areas. The abovementioned HPTEs used to start with strong and sudden freshwater discharges after relatively long periods of very low freshwater inflow and caused significant decreases in
abundances of anchovy recruits and the mysid Mesopodopsis slabberi, its main prey
(Figure 4).
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ICES WGSPEC REPORT 2012
Portuguese Spring Acoustic Surveys
Anchovy in Sub-division IXa-South
Number (thousands)
4000000
3500000
3000000
2500000
Age 1
2000000
Age 2
1500000
Age 3
1000000
500000
0
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
Year
Figure 3. Age structured estimates of GoC anchovy abundance from the Portuguese acoustic survey series. The null estimates for the 2011 Portuguese survey should be considered with caution
(ICES, 2011).
All of these evidences confirm that the GoC anchovy stock relies on recruits to persist
and, therefore, is highly vulnerable to ocean processes and totally controlled by environment fluctuations.
ICES WGSPEC REPORT 2012
| 23
Figure 4. Monthly/daily mean values of environmental variables (water temperature, salinity,
rainfall, freshwater inflow, and turbidity), mysid and anchovy recruits densities in the Guadalquivir Estuary from May 1997 to February 2009, and winter NAO index values for the same
period. F, February, M, May, A, August, N, November. Shaded symbols, samples collected during
HPTEs (composite figure from González-Ortegón et al., 2010).
References
Baldó, F., P. Drake, 2002. A multivariate approach to the feeding habits of small fishes in the
Guadalquivir Estuary. Journal of Fish Biology 61(Suppl. A): 21-32.
Baldó, F., E. García-Isarch, M. P. Jiménez, Z. Romero, A. Sánchez-Lamadrid, I. A. Catalán, 2006.
Spatial and temporal distribution of the early life stages of three commercial fish species in
the North Eastern shelf of the Gulf of Cádiz. Deep Sea Research Part II 53 (11–13): 1391–
1401.
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ICES WGSPEC REPORT 2012
Criado-Aldeanueva, F., J. García-Lafuente, J. M. Vargas, J. Del Rio, A. Vázquez, A. Reul, A.
Sánchez, 2006. Distribution and circulation of water masses in the Gulf of Cadiz from in
situ observations. Deep Sea Res. Part II, 53(11–13): 1144–1160.
Drake, P., A. Borlán, E. González-Ortegón, F. Baldó, C. Vilas, C. Fernández-Delgado, 2007. Spatio-temporal distribution of early life stages of the European anchovy Engraulis encrasicolus
L. within a European temperate estuary with regulated freshwater inflow: effects of environmental variables. Journal of Fish Biology 70, 1689–1709.
Fernández-Delgado, C., F. Baldó, F., C. Vilas, D. García-González, J. A. Cuesta, E. GonzálezOrtegón, P. Drake, 2007. Effects of the river discharge management on the nursery function of the Guadalquivir river estuary (SW Spain). Hydrobiologia 587: 125–136.
Folkard, A., P. Davies, A. Fiúza, I. Ambar, 1997. Remotely sensed sea surface thermal patterns
in the Gulf of Cadiz and the Strait of Gibraltar: Variability, correlations, and relationships
with the surface wind field. J. Geophys. Res., 102 (C3): 5669–5683.
García-Lafuente, J., J. Ruiz, 2007. The Gulf of Cadiz pelagic ecosystem: A review. Prog. Oceanogr., 74: 228–251.
García-Lafuente, J., J. Delgado, F. Criado-Aldeanueva, M. Bruno, J. del Rio, J. M. Vargas, 2006.
Water mass circulation on the continental shelf of the Gulf of Cadiz. Deep Sea Res. Part II,
53 (11–13): 1182–197.
ICES, 2011. Report of the Working Group on Anchovy and Sardine (WGANSA), 24-28 June
2011, Vigo, Spain. ICES CM 2011/ACOM: 16. 462 pp.
Navarro, G., J. Ruiz, 2006. Spatial and temporal variability of phytoplankton in the Gulf of
Cadiz through remote sensing images. Deep Sea Res. Part II, 53 (11–13): 1241–1260.
Navarro, G., F. J. Gutiérrez, M. Díez-Minguito, M. A. Losada, J. Ruiz, 2011. Temporal and spatial variability in the Guadalquivir estuary: a challenge for real-time telemetry. Ocean Dynamics 61 (6): 753-765.
Peliz, A., A. Fiúza, 1999. Temporal and spatial variability of CZCS derived phytoplankton
pigment concentrations off western Iberian Peninsula. Int. J. Remote Sens., 20 (7): 1363–
1403.
Peliz, A., P. Marchesiello, A. M. P. Santos, J. Dubert, A. Teles-Machado, M. Marta-Almeida, Le
Cann, 2009. Surface circulation in the Gulf of Cadiz: 2. Inflow-outflow coupling and the
Gulf of Cadiz slope current. J. Geophys. Res., 114, C03011, doi: 10.1029/2008JC004771.
Prieto, L., G. Navarro, S. Rodríguez-Gálvez, I. E. Huertas, J. M. Naranjo, J. Ruiz, 2009. Oceanographic and meteorological forcing of the pelagic ecosystem on the Gulf of Cadiz shelf
(SW Iberian Peninsula). Continental Shelf Research 29: 2122–2137.
Relvas, P., E. Barton, 2002. Mesoscale patterns in the Cape São Vicente (Iberian Peninsula) upwelling region. J. Geophys. Res., 107 (C10): 3164, doi: 10.1029/2000JC000456.
Ruiz, J., E. García-Isarch, G. Navarro, L. Prieto, A. Juárez, J. L. Muñoz, A. Sánchez-Lamadrid, S.
Rodríguez, J. M. Naranjo, F. Baldó, 2006. Meteorological forcing and ocean dynamics controlling Engraulis encrasicolus early life stages and catches in the Gulf of Cadiz. Deep Sea
Res. Part II, 53 (11–13): 1363–1376.
Ruiz, J., R. González-Quirós, L. Prieto, G. Navarro, 2009. A Bayesian model for anchovy (Engraulis encrasicolus): the combined forcing of man and environment. Fish. Oceanogr. 18(1):
62-76.
Sánchez, R., P. Relvas. 2003. Spring-summer climatological circulation in the upper layer in the
region of Cape St. Vincent, Southwest Portugal, ICES Journal of Marine Science, 60: 1232–
1250, doi:10.1016/S1054–3139(03)00137-1.
Sánchez, R., E. Mason, P. Relvas, A. da Silva, A. Peliz, 2006. On the inshore circulation in the
northern Gulf of Cadiz, southern Portuguese shelf, Deep Sea Res. Part II, 53 (11–13): 1198–
1218.
ICES WGSPEC REPORT 2012
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González-Ortegón, E., M. D. Subida, J. A. Cuesta , A. M. Arias, C. Fernández-Delgado, P.
Drake. The impact of extreme turbidity events on the nursery function of a temperate
European estuary with regulated freshwater inflow. Estuarine, Coastal and Shelf Science
87: 311–324.
3.6
Small pelagic fish research in the Mediterranean by the Spanish Institute
of Oceanography: available data series for a climatic analysis
A. García, A. Giraldez
The Spanish Institute of Oceanography (IEO) as the official institution in charge of
maritime affairs regarding fisheries and marine environmental research has the necessary infrastructure to provide assessment results to the Spanish administration. The
small pelagic fisheries research division of the Mediterranean counts on different projects whose objectives have direct or indirect relationship with small pelagic fish research studies.
In first place, the evaluation of small pelagics is through the implementation of direct
methods by echo-acoustic tracking surveys and by indirect methods using age-based
modelling approaches. The project co-funded by the UE MEDIAS (Mediterranean
Acoustics Surveys) covers on a yearly basis the Geographical Subarea GSA06 of the
General Fisheries Council of the Mediterrean (GFCM) (Northen Spain) and partly
GSA01 (Northern Alboran Sea); (Figure 1). The echo-acoustic surveys undertaken by
the IEO represent the longest time series of annual surveys of the Mediterranean, dating back as far as 1990.
Fig. 1. GFCM Geographical Statistical divisions
The Data Collection Program of the IEO funded by the UE contains the information
gathered from the fisheries, sampling surveys, and observers’ embarkment surveys.
Moreover, the ichthyoplankton group of the oceanographic centres of Málaga, Madrid and the Baleares provide expertise and collaboration in aspects related with
early life history aspects of small pelagic fish ecology, as well as with the delimitation
of spawning grounds by the use of CUFES (Continuous Underwater Fish Egg Sampler). Much of this collaboration has been envisaged in the framework of the project
MEDIAS. Furthermore, projects financed by the Spanish National Research Council
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ICES WGSPEC REPORT 2012
have allowed to study the early life trophic food web dynamics in key larval concentration sites off the SW Mediterranean coasts (TROFOALBORAN project).
The longest time series available with regards to small pelagic fisheries refer to the
volume of landings. Some of these series date back as far as 1945. These landing data
series were made available during the ICES Workshop on Small Pelagic Fishes, their
Ecosystems and Climate Impact and used for analysis of climatic influence on stock
fluctuations. Although one might think that landings are not the most ideal data set
for this sort of analysis, important magnitudes in landing variability cannot be solely
attributed to an increase or decrease of effort. Furthermore, the expert’s advice on
these changes was considered essential.
Small pelagic stocks off the Spanish Mediterranean coasts are included in two main
GFCM statistical divisions: GSA01 which corresponds to the Alborán Sea and GSA06
which corresponds to the northern area generically called Tramontana. The main species found in these areas correspond to sardine (Sardina pilchardus), anchovy (Engraulis encrasicolus) and sardinella (Sardinella aurita). The statistical divisions also
correspond to distinct characteristics in relation to hydrography, bottom topography
and biological features. The main mass of small pelagic stocks is within GSA06 due
to its ample shelf whose hydrography and productivity is highly influenced by the
outflows of the Rhone and Ebro rivers. Opposed to this situation, the Alborán Sea
with its narrow continental shelf where river outflow is negligible in comparison
with the NW Mediterranean and whose productivity is highly influenced by the incoming surface circulation of Atlantic waters.
An analysis of the sardine landings from both areas shows contrastingly distinct patterns (Figure 2). While the Alborán Sea’s landings show strong fluctuations since the
sixties, the landings of GSA06 increased till mid-1990. This increase was mainly
caused by the progressive increase of fishing effort carried out during the mideighties. Nonetheless, although fishing effort decreased progressively from the midnineties onward, GSA06 shows a significant decreasing trend to the present time in
opposition to the yearly fluctuations that are observed in GSA01.
With regards to anchovy, the same type of differences occurs in the comparison between both statistical areas (Figure 3). From the mid-1970 to the mid-1980, anchovy
resources were very abundant in both areas mainly due to the fact that a great part of
the exploitation was undertaken in waters of the Moroccan coasts. Nonetheless, in
1985, a collapse of this resource occurred in both areas. The state of depletion of the
anchovy resource has been maintained since then in GSA01. The anchovy resources
off the Tramontana region off the northern coasts (GSA06) recovered to its former levels in the late eighties till the mid-nineties when the species began to show another
decline. With the exception of the good 2001 recruitment shown in both statistical
divisions, the anchovy resource has shown a progressive decline till 2008. Within this
rather sombre perspective, the resource has shown two good recruitments during
2009 and 2010.
ICES WGSPEC REPORT 2012
| 27
Figure 2. Sardine landing data series from 1960 to 2010.
ANCHOVY
30000
GSA 01
25000
Tons
15000
10000
GSA 06
5000
2008
2005
2002
1999
1996
1993
1990
1987
1984
1981
1978
1975
1972
1969
1966
1963
1960
0
Tons
20000
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0
YEARS
Figure 3. Anchovy landing data series from 1960 to 2010.
To examine the causes of such variability, various aspects of the reproductive biology
of anchovy (Engraulis encrasicolus L.) in the Alboran Sea were studied for two time
periods separated by 11 years: 1989–1992 and 2003–2007 (Giraldez, A. 1). Correlation
between the gonadosomatic index (GSI) and sea surface temperature was assessed by
GAMs models. There was a significant positive correlation between GSI and sea surface temperature (p <0.001). Temperatures in the fourth quarter of the second period
1
Giráldez, A. 2009. Study on the temporal variability of reproductive parameters of anchovy
(Engraulis encrasicolus L.) in the Alboran Sea. Memoria DEA Universidad de Málaga.
GSA0606
GSA
BOQUERON
GSA
GSA0101
BOQUERÓN
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ICES WGSPEC REPORT 2012
(2004–2007) were significantly higher than those for the first period (1990–1992), resulting in significantly higher GSI values in that quarter and period.
The GSI shows a more prolonged period of reproduction along the year in the period
2004–2007 in comparison with the period 1990–1992 (Figure 4). The condition factor
(CF) showed a very different profile in both periods (Figure 5), which was not correlated with either the concentration of chlorophyll in the Alboran Sea and the GSI. A
change in the nutritional status of anchovy is observed. During the first period, condition factor (CF) changes were sharper and more acute indicating environmentally
induced changes, while during the second period a subsistence strategy seems to
have prevailed.
1990-92
2004-07
Índice Gonadosomático
0.0700
0.0600
0.0500
0.0400
0.0300
0.0200
0.0100
0.0000
-0.0100
1
2
3
4
5
6
7
8
9
10
11
12
Mes
Figure 4. Mean monthly GSI between the two periods with standard deviations.
ICES WGSPEC REPORT 2012
| 29
Figure 5. Condition factor for each of the years and monthly means for each period.
The decrease of sardine and anchovy stocks off the Mediterranean since the midnineties was accompanied by an increase of another clupeoid, Sardinella aurita, which
was more pronounced in the NW Mediterranean region than in the Alborán Sea.
Nonetheless, recovery of landing data series since 1945 shows that this species had
shown similar peak periods of abundance from the mid-forties to the late fifties in the
Mediterranean (Figure 6). S. aurita was not the only species that increased during the
last period of the series. Data from the acoustic surveys undertaken on a yearly basis
also observed the increase of medium sized pelagics species, among which different
Mediterranean species of Trachurus stand out, together with Scomber sp. and Boops
boops. Thus, it seems that the pelagic domain shifted in terms of relative composition
(Internal IEO Reports of Acoustic surveys).
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ICES WGSPEC REPORT 2012
0,4
12000
Sardinella aurita
0,2
8000
0,1
0
6000
-0,1
4000
AMO index
LANDINGS (tons)
0,3
AMO
10000
-0,2
2000
-0,3
2010
2005
2000
1995
1990
1985
1980
1975
1970
1965
1960
1955
1950
-0,4
1945
0
Years
Figure 6. Sardinella aurita landings data series together with the mean annual value of the AMO.
In view of the signals of stock variability as shown by the historical data series of
landings, an analysis of climatic indices with the oscillations of the catch was undertaken. The most adequate climatic index is the Atlantic Multidecadal Oscillation
(AMO); (Figure 6). Positive values of this index are related with warm periods while
negative values respond to cool climatic regimes. The increase of S. aurita, a tropical
species preferably inclined to warmer temperatures, are clearly associated with the
warm AMO periods of the Mediterranean. Inversely, anchovy showed highest abundances in the period corresponding to cooler weather regimes in the Mediterranean
(Figure 7).
0,4
60000
Engraulis encrasicolus
AMO
0,3
0,2
40000
0,1
0
30000
-0,1
20000
-0,2
10000
-0,3
2010
2005
2000
1995
1990
1985
1980
1975
1970
1965
1960
1955
1950
-0,4
1945
0
Years
Figure 7. Engraulis encrasicolus landings data series together with the mean annual value of the
AMO.
AMO index
LANDINGS (tons)
50000
ICES WGSPEC REPORT 2012
| 31
The relationship of AMO with sardine fluctuations was not that clear (Figure 8). It
was discussed that this may be due to the fact that not all species respond in the same
manner to climatic changes.
0,4
70000
Sardina pilchardus
AMO
0,3
0,1
40000
0
30000
-0,1
20000
-0,2
2010
2005
2000
1995
1990
1985
1980
1975
1970
1965
-0,4
1960
0
1955
-0,3
1950
10000
Years
Figure 8. Sardina pilchardus landings data series together with the mean annual value of the
AMO.
3.7
Environmental impacts on anchovies; sardines and sardinellas in the north
western Mediterranean
I.Palomera
The small pelagic fish inhabiting the NW Mediterranean Sea are European anchovy
(Engraulis encrasicolus L.), sardine (Sardina pilchardus Walb.), round sardinella (Sardinella aurita) and sprat (Sprattus sprattus). These four species represent almost 50% of
the total fish landings in the whole Mediterranean. In the NW Mediterranean Sea,
anchovy and sardine are the most important species in terms of both biomass and
commercial interest. Round sardinella and sprat are also present at lower levels of
biomass but they are of little commercial interest.
The commercial exploitation of small pelagic fish in the NW Mediterranean has been
significant since the early 1940s. Catches were initially dominated by sardine, probably due to its coastal distribution. Improvements in fishing technology in the 1960s
allowed fishing to be carried out offshore and anchovy catches increased substantially, in parallel with a continuous increase in sardine catches. Although sardine
makes up the largest share, anchovy reaches a higher price in the market and is thus
more important and subject to heavier fishing pressure.
AMO index
0,2
50000
1945
LANDINGS (tons)
60000
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ICES WGSPEC REPORT 2012
Scientific acoustic surveys are routinely performed in the NW Mediterranean coast
by Spanish and French research groups to assess the biomass of anchovy and sardine.
Daily Egg Production Methods (DEPM) have also been sporadically applied in the
region to anchovy spawning stocks in the Gulf of Lions and the Catalan Sea (Palomera et al. 2007).
Biomass data from the Gulf of Lions since the 1990s show a divergent trend for anchovy and sardine, with a peak in different years. But nowadays both species have
very low levels of biomass. In the Catalan Sea both species are declining: the sardine
from the 1990s on , and the anchovy from 2001 on. The sardine has now very low
biomass levels and the anchovy seems to stabilize at low levels in 2009. Both regions
show a decline in anchovy and sardine landings from the middle 1990s, which is
more marked in the Catalan Sea.
In the NW Mediterranean production of sardine and anchovy is clearly influenced by
changes in the environment (e.g. river runoff and wind mixing: Lloret et al., 2002 and
2004). In the South Catalan Sea a negative relationship of sardine biomass and the
mean SST has been also noticed during the spawning months, probably related with
the colder water conditions required by sardine for spawning and larval development. The observed temperature increase during warm periods, with higher sea water temperatures during winter time from the 1970s on, had probably a negative
impact on sardine spawning and recruitment (Palomera et al., 2007).
ICES WGSPEC REPORT 2012
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At the global scale, two temperature regimes are evident in the NW Mediterranean
between 1950 and 2003: the period 1950–1980, characterized by negative air temperature anomalies, and the period 1981–2003, with positive anomalies. Small pelagic fish
biomasses in the NW Mediterranean region seem to have reacted to a global warming
trend, as observed by a decrease in the abundance of sardine and anchovy and a increase in the distribution area and abundances of round sardinella (Sabatés et al.
2006).
References
Lloret, J., Lleonart J, Sole I, Fromentin J-M. 2001. Fluctuations of landings and environmental
conditions in the north-western Mediterranean Sea. Fish Oceanogr 10:33-50.
Lloret, J., Palomera I, Salat J, Sole I. 2004. Impact of freshwater input and wind on landings of
anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in shelf waters surrounding the Ebre (Ebro) River delta (north-western Mediterranean). Fisheries Oceanogr 13:102–
110.
Palomera, I., Olivar MP, Salat J, Sabates A, Coll M, Garcia A, Morales-Nin B. 2007. Small pelagic fish in the NW Mediterranean Sea: an ecological review. Prog Oceanogr 74:377-396.
Sabatés, A., Martín, P., Lloret, J. & Raya, V. 2006Sea warming and fish distribution: the case of
the small pelagic fish, Sardinella aurita, in the western Mediterranean. Global Change Biology. 12: 2209-2219.
3.8
Population dynamics of small pelagic species in the Adriatic Sea: Stock
Assessment Models and Environmental Factors
P. Carpi, A. Santojanni, A. Russo
The Adriatic Sea is a semi-enclosed basin, which communicates with the rest of the
Mediterranean Sea through the Otranto Channel. The overall circulation is driven by
the Po River outflow, that is the largest fresh water input of the basin, by the surface
fluxes acting at the surface, which force the circulation to be seasonal, and by the external flow exchange with the Mediterranean, that brings heat and salty waters into
the circulation.
The Italian fishery of small pelagic (mainly anchovy and sardine) is one of the most
productive fisheries in the Adriatic: in the 2008, for example, this fishery accounted
for about the 31% of the overall national catches. In the early 80s the landings reached
the highest value of 54 000 t: the main reason for these high catches was a regulation
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ICES WGSPEC REPORT 2012
from the Comunità Economica Europea (CEE) that entrusted an Italian agency to buy
the unsold catches from the fishermen for a price sometimes higher than the market
price itself.
Since 1975, The CNR-ISMAR of Ancona has been collecting data on landings and
morphometric parameters of small pelagics, covering the main ports along the Italian
coast and gathering information from the ports on the eastern side of the basin (i.e.
from Yugoslavia first, then Slovenia and Croatia). The landings of anchovy dropped
to really low values in the 1987, reaching the minimum values of 5900 t in the 1988,
while sardine landings started a slow decrease in the late 1980s, reaching the minimum values in the 2006; after this year the catch started increasing again.
The preliminary results presented here refer only to the anchovy stock.
The total landings were treated in order to get catch at age time series and to obtain
the input data necessary to estimate the total biomass at sea by the means of population dynamics methods (i.e. Virtual Population Analysis and Integrated Catch Analysis).
Once the annual recruitment and the total biomass at sea were estimated, the data
were correlated to some environmental variables (i.e. SST, Po river flow rate, q coefficient which is the heat flux at the surface, NAO index and Mediterranean Oscillation
Index (MOI)). Each environmental variable was averaged along the whole area and
each year has been divided into 3 months periods. Besides, one year time lag between
environment and recruitment was considered in the comparisons.
Autocorrelation between variables has been tested. Principal Component Analysis
(PCA) and Redundancy Analysis (RDA) methods were chosen to explore the internal
structure of the data. Both techniques stressed the importance of the SST and the Po
river flow rate and detected a clear jump between the 1987/1988 (the years of the collapse) and the previous and following years.
Dynamic Factor Analysis (DFA) from Zuur et al. (2003) has been performed as well:
this technique has been designed to work in time series analysis, to find latent common trends in the data. Two common trends have been detected, but the model has
still to be improved.
General Linear Models (GLM) and Generalized Additive Models (GAM) have been
developed: the results were consistent with previous studies (i.e.: significant relationship found for the SST, the Po river outflow rate and the NAO (Santojanni et al.,
2006)). In addition, the q coefficient was significant in spring, and contributed significantly to the model in the fall months.
Improvements to the models used are still necessary and some questions have to be
investigated, such as: is the extension of the anchovy spawning season observed in
the last years due to the increasing trend of the observed temperature?
References
Santojanni, A., Cingolani, N., Arneri, E., Belardinelli, A., Giannetti, G., Colella, S., and Donato,
F. 2006a. Use of an exploitation rate threshold in the management of anchovy and sardine
stocks in the adriatic sea. Biologia Marina Mediterranea, 13(3):98–111.
Santojanni, A., Arneri, E., Bernardini, V., Cingolani, N., Marco, M. D., and Russo, A. 2006b.
Effects of environmental variables on recruitment of anchovy in the adriatic sea. Climate
Research, 31:181–193.
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Santojanni, A., Arneri, E., Barry, C., Belardinelli, A., Cingolani, N., Giannetti, G., and Kirkwood, G. 2003. Trends of anchovy (engraulis encrasicolus, l. biomass in the northern and
central Adriatic Sea. Scientia Marina, 67(3):327–340.
Zuur, A. F., Tuck, I. D., and Bailey, N. 2003. Dynamic factor analysis to estimate common
trends in fisheries time series. Canadian Journal of Fisheries and Aquatic Sciences, 60:542–
552.
3.9
Biomass evaluation of anchovy ( E. encrasicolus), sardine ( S. pilchardus)
and sprat ( S. sprattus ) in the western Adriatic Sea by means of acoustics
and preliminary analysis of possible relationships with environmental parameters
A. De Felice
Acoustic surveys on small pelagic fish in the western side of the Adriatic Sea were
carried out by ISMAR-CNR of Ancona since 1976 within the framework of several
national and one EU (European Union) projects. From 2009 onwards, the above mentioned surveys are integrated into a group of coordinated acoustic surveys on small
pelagic fish which are funded by the EU in cooperation with local Ministries under
the MEDIAS framework (pan-MEDIterranean Acoustic Surveys). These mandatory
MEDIAS acoustic surveys incorporate the joint work of many Mediterranean re-
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search institutions form several countries (Italy, Greece, Spain, France, Malta, Slovenia); also, Romania and Bulgaria joined the group and adopted the protocol for
planned surveys in the Black Sea.
In addition to the MEDIAS surveys, other acoustic surveys to estimate small pelagic
fish biomass were carried out in 2002, 2004 and 2005 on the continental shelf off Montenegro with the sponsorship first of Montenegro Government and then of the FAO
AdriaMed Project (since 2005); afterwards the study area was extended to Albania in
2008, 2010 and 2011.
In synchrony with the acoustic survey an eggs and larvae survey is carried out on
anchovy since 2005 while in the western side of GSA 18 this is carried out since 2010
in order to estimate Spawning Stock Biomass of anchovy by the Daily Egg Production
Method.
The main target species of the acoustic surveys in the Adriatic are E. encrasicolus and
S. pilchardus; small pelagics of secondary importance are S. sprattus, S. scombrus, S.
japonicus, T. trachurus, T. mediterraneus, S. aurita, B. boops, Spicara spp. etc..
The survey design is made up by a grid of parallel transects, perpendicular to the
coastline; inter-transect distance is 10 nautical miles, 8 in areas in which the continental shelf is narrow or where political boundaries are present.
In the Adriatic Sea, due to the Treaty of Osimo (1978), transects cannot go further
than the Mid Line that subdivides this sea in two equal parts. Near Pomo Pits and
along the Apulia coasts the limit is given by the 200 metres bathymetry (Figure 1).
Acoustic data are logged by the scientific echosounder Simrad EK60 and analyzed
with Myriax Echoview software.
The geographical position is derived through a GPS system; the vessel speed is 9.5
knots during the survey.
The echosurvey is made every year during summer (July–September) since 1976 in
the northern part of the Adriatic Sea (Trieste-Giulanova) and since 1987 in the central
and southern Adriatic Sea (Giulianova-Brindisi).
The geographic Sub Area 17 (FAO subdivision) is covered in September in coordination with the Croatian survey carried out in the eastern side of the Adriatic Sea. This
survey also covers Slovenian waters in cooperation with the Fishery Research Institute of Ljubljana. Geographic Sub Area 18 is covered in July for both the Italian and
the Montenegro-Albania side, in cooperation with the Institute of Marine Biology of
Kotor (Montenegro) and with the University of Tirane (Albania).
The main results of an acoustic survey are biomass estimates for the target species in
the study area and their spatial distribution.
Some preliminary analysis dealing with the trends of anchovies and sardines and the
environmental parameters were tried in the past and were the subject of some publications (Azzali et al., 2002; Azzali et al., 2007).
The main conclusions of these preliminary analyses were:
1 ) Pelagic biomass fluctuations show cycles of 3–5 years that are probably
traceable to macro-scale climatic factors; the bigger variations in the biomass of single species (anchovies, sardines, sprats) are characterized by
peaks and drops that seem less regular with respect to total pelagic biomass;
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2 ) The anchovy stock collapse (climax in 1987) corresponds to the period
(1984–1991) in which the average mean of SST in the Adriatic Sea (data
from SeaWIFS sensor reprocessed and adapted at ISAC-CNR of Bologna
by means of TeraScan software) show values that are much lower with respect to contiguous years; this could have had a negative influence on larvae survival.
Another analysis that was attempted consisted in a correlation test between the anchovy biomass trend in the northern Adriatic Sea and the mean seasonal surface
temperature data (Leonori et al., 2009). In the Northern Adriatic Sea anchovy biomass
showed a positive correlation with mean spring surface temperature (March, April,
May), with a time lag of one year. The correlation was highly significant (r = 0.70,
p<0.01). Spring SST was minimum in 1986 at the beginning of anchovy stock collapse
(Figure 2).
The situation is similar in the Central and Southern Adriatic Sea (r = 0.77, p<0.01).
Sardine biomass did not show a clear correlation with mean surface temperature of
any season.
Azzali M., De Felice A., Cosimi G., Luna M., Parmiggiani F., 2002. The state of the
Adriatic Sea centered on the small pelagic fish populations. P.S.Z.N.: Marine Ecology,
23, Supplement I (2002), 78-91
Azzali M., Leonori I., De Felice A. 2007. Fluttuazioni spazio-temporali della biomassa dei piccoli pelagici nel Mare Adriatico in relazione ai cambiamenti climatici. In Clima e Cambiamenti Climatici le attività di ricerca del CNR, Ed. Consiglio Nazionale delle Ricerche, pp.
547-550.
Leonori I., Azzali M., De Felice A., Parmiggiani F., Marini M., Grilli F., Gramolini R. 2009.
Small pelagic fish biomass in relation to environmental parameters in the Adriatic Sea.
Proceedings of AIOL-SItE Congress – 2009.
Figure 1. Survey design of the acoustic survey in the western Adriatic Sea.
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Figure 2. Above in green colour: trend of spring SST Survey design of the acoustic survey in the
western Adriatic Sea; below in black colour: trend of anchovy biomass in north-western Adriatic
Sea.
3.10 Impact of climate variability on small pelagic fishes in the Eastern
Mediterranean
A. Tsikliras, A.G. Harlioglu
The landings of the 6 most important clupeiform species (Order: Clupeiformes) in the
eastern Mediterranean Sea (Aegean and Levantine Seas) averaged around 205 000 t
(±23 000 t) between 2000–2008 accounted for over 30% of the total catches. Five of
them are members of the Clupeidae family (European pilchard or sardine Sardina
pilchardus, round sardinella Sardinella aurita, Madeiran sardinella Sardinella maderensis,
sprat Sprattus sprattus and red-eye round herring Etrumeus teres) and one belongs to
the Engraulidae family (European anchovy Engraulis encrasicolus). As they share similar morphological characteristics, the catches of these species are often recorded/reported aggregated. Thus, the effect of potential climate variability on the
distribution, biomass and population characteristics of a species may be masked.
Climatic variability, especially documented by sea temperature changes, has been
shown to affect the geographic/bathymetric distribution and biomass, as well as certain population characteristics (e.g. Alheit et al., 2012, Prog. Oceanogr. 96: 128-139).
Some species, such as the sardinellas and red-eye round herring, have benefitted
from temperature increase and expanded their distribution, while some others reduced their area of distribution (?), such as sprat and sardine. Indeed, round sardinella has expanded northwards in the Aegean Sea (Tsikliras, 2008, Mar. Biol. Res. 4:
477-481) and its catches have increased since 1990 (Figure 1). The combined catches of
round and Madeiran sardinella (i.e. Sardinella spp.) have also increased in Levantine
Sea since 1975 (data not shown). Alarming biomass declines and/or contractions of
the area of distribution of psychrophilous species have not yet been observed across
the eastern Mediterranean Sea.
Historical records of round sardinella catches in the Aegean (1928–1948: available in
Moutopoulos & Stergiou, 2011, Acta Adriat. 52: 183-200) show that its biomass in the
area was higher during this early period when compared to the time span from 19641990 (Figure 1). The round sardinella catches (plotted as a ratio of round sardinella
over combined sardine and anchovy catches, in order to correct for fishing effort) in
the Aegean Sea are generally higher during the warm periods of the Atlantic Multidecadal Oscillation (AMO: Enfield et al., 2001, Geophys. Res. Lett. 28: 2077–2080)
(Figure 1, top panel).
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Atl
an
tic
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ulti
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ca
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os
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(A
M
O)
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sa
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Figure 1. Atlantic Multidecadal Oscillation (AMO) for the period 1928–2009. Corrected (blue line)
and uncorrected (red line) (top panel) and the ratio of round sardinella to combined sardine and
anchovy catches of the Aegean Sea for the same period (bottom panel). Note that no catch data for
round sardinella exists for the period between 1949–1963.
3.11 Anchovy: environment, biology and recruitment in the Bay of Biscay
U. Cotano, A. Uriarte
Favourable mechanisms for the recruitment of the European anchovy (Engraulis encrasicolus) in the Bay of Biscay have been traditionally interpreted in terms of the concept developed by Bakun (1996): the triad of retention, enrichment and concentration.
Until the series of poor recruitment experienced by the anchovy fishery beginning in
2002, the upwelling strength and the stability of the thermal stratification had been
pointed out as the most relevant environmental factors enhancing the anchovy recruitment, whilst the issue of how much drifting out or retention over the shelf was
controversial among scientists (Borja et al., 1996, 1998; Uriarte, 2001; Allain et al., 2001,
2007).
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Higher recruitments are associated with northeasterly winds enhancing upwelling
(Borja et al., 1996, 1998, 2008; Allain et al., 2001), and higher productivity beyond that
induced by river influence. However, northeasterly winds increased transport off the
French shelf which contains the major spawning grounds. In the frame of a ‘‘Bakun
triad’’ interpretation of the recruitment, the anchovy juveniles off the shelf would
most likely be lost from the population but given the particular geography of the Bay
of Biscay this is not necessarily true as a southwestern drift from the French shelf can
lead through oceanic waters towards the Spanish shelf, which may facilitate a later
return to the French shelf (Borja et al. 1998; Irigoien et al. 2007). In addition, several
recent observations do not match with the idea of a detrimental effect of the transport
off the French shelf: during recent years there is no clear relationship between zooplankton abundance over the shelf and anchovy recruitment (Irigoien, 2009); feeding
activity of juvenile and adult anchovy may be even higher in oceanic waters (Plounevez and Champalbert, 1999, Bachiller 2012, submitted); both scientific studies and live
bait tuna fishery data reported consistent observations of anchovy juveniles in oceanic waters (Uriarte et al. 2001; Carrera et al. 2006; Irigoien et al., 2007, 2008, Aldanondo et al., 2010); growth rates for anchovy larvae and juvenile are not lower in
oceanic waters (Cotano, 2008, Irigoien, 2007, 2008; Aldanondo et al., 2010) and, finally,
most recent environmental models have shown than the westwards transport has a
significant positive effect on anchovy recruitment (Borja et al., 2008, Irigoien, 2009).
On the other hand, larval dispersal during summer has been shown as a limiting factor for anchovy recruitment in IBM modelization (Allain et al., 2007, Hure et al., 2007
and Petitgas et al., 2011).
The relatively high productivity of oceanic waters in the Bay of Biscay associated
with different physical events like shelf-break fronts or eddies, the relatively high
abundance of bigger zooplankton size-classes, the theoretically higher capability of
anchovies to capture zooplankton preys in less turbid waters far from coastal areas
and the lower concentration of potential predators off the shelf could help to explain
the survival rates of anchovy larvae and juveniles observed to be associated with oceanic waters during their recruitment process, as Uriarte et al. (2001) had previously
proposed .
Therefore, although different environmental factors help to explain a relatively high
percentage of variability associated with anchovy recruitment in the Bay of Biscay
(Fernandes et al. 2010), there is still a lack of understanding on how some environmental processes affect the survival of early life stages and anchovy recruitment; especially those related to the retention-transport of anchovy larvae off the shelf. In any
case, the “enrichment-retention-survival” recruitment theory associated to upwelling
events cannot be interpreted in a strict way in the Bay of Biscay for anchovy.
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Figure 3.11. Scheme of the proposed spatial pattern of recruitment of the Bay of Biscay anchovy.
Adapted from Uriarte et al. (2001).
3.12 Impact of climate variability on herring and capelin in northern seas
A. Slotte
The Institute of Marine Research in Norway has many cross sections from the coast
into the Barents Sea, Norwegian Sea, North Sea, and Skagerak, which are surveyed
several times a year to study environmental conditions (Figure 1). In addition, there
are fixed coastal monitoring stations along the coast with weekly CTD sampling
down to 200 m depth. These sources all pick up the AMO signal (Figure 2); (Skagseth
et al. 2008).
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Figure 1. Overview of IMR’s large scale monitoring of environmental conditions. Several cross
sections covered several times every year. Coastal monitoring stations along the coast, with sampling every week. In addition the North Sea, Norwegian Sea, Barents Sea are covered twice every
year during international ecosystem surveys.
Figure 2. Comparison between historic fluctuations in the temperature from the Kola section in
the Barents Sea and the AMO-index (From Skagseth et al. 2008).
Warm periods are characterized by increased recruitment and growing stocks in the
Northern Seas. The times series on NSS herring is unique, giving SSB/catch (Figure 3)
and recruitment (Figure 4) back to 1907. There was a clear increase in recruitment and
growing SSB from 1.5 million t in 1907 to 16 million t in 1945, along with increasing
temperatures in the area. After this the stock was overfished during a period with
cooling climate, resulting in a total collapse of the stock from levels at 16 million t to
levels below 0.1 million t. Simulations have indicated that, if the current harvest rule
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would have been used also during the 1930s–1960s, the stock would still have decreased during the cooling period, but it would have stabilized around 5 million t
(Røttingen and Tjelmeland, 2011). From 1970s onwards there has been a warming
period, and the stock increased due to very high recruitment in 1983. Other good recruitment years in 1991/1992, 1998/1999, 2002 and 2004 all happened during peaks in
the temperature and AMO signal. This has led to SBB levels between 5 and 10 million
t since the late 1990s, but after a period with low recruitment after 2004, the stock is
now decreasing.
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Figure 3 . Historic fluctuations in SSB and landing of NSS herring.
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Figure 4. Historic fluctuations in recruitment (R0) of NSS herring.
Another abundant small pelagic in the Northern Seas is the capelin, which is the key
species in the Barents Sea. The recruitment of this stock is related to sea temperatures
in winter and spring, but recruitment failures are mostly caused by predation on larval stages from immature NSS herring using the Barents Sea as a nursery area, and
by predation from Northeast Arctic cod, Figure 5 (Hjermann et al. 2010).
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Figure 5. Abundance of capelin (Mallotus villosus) cohorts from 1974 to 2006 (year of spawning)
in stages 1–4. Parent generations (stage 1) are represented by biomass of maturing fish in September. The two bar plots at the bottom show the annual biomass of the capelin predators cod
(Gadus morhua) (ages 3–6, solid bars; ages 7–13, shaded bars) and young herring (Clupea harengus). From Hjerman et al. 2010.
Given equal stock size the distribution of capelin during the feeding season changes
significantly with ocean temperature (Ingvaldsen and Gjøsæter, 2011); 1oC increase in
temperature results in 125 000 km2 increase in distribution area and a 150 km northward shift of the high-concentration areas. This is linked to changes in ice cover decreasing in recent years (Figure 6); (Ingvaldsen et al. 2011).
Figure 6. Observed changes in winter ice edge in the Barent Sea in late winter, 1997–2009.
References
Ingvaldsen, R. and Gjøsæter, H. 2011. Impact of marine climate variability and stock size on
the distribution area of Barents Sea capelin. In IMR/PINRO joint report series 2/2011: Climate change and effects on the Barents Sea marine living resources 15th RussianNorwegian Symposium Longyearbyen, 7-8 September 2011, pp 279-280.
ICES WGSPEC REPORT 2012
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Ingvaldsen, R., Lind, S. and Loeng, H. 2011. Barents Sea climate variability during the last decade. In IMR/PINRO joint report series 2/2011: Climate change and effects on the Barents
Sea marine living resources 15th Russian-Norwegian Symposium Longyearbyen, 7-8 September 2011, pp 279-280.
Hjermann, D. Ø., Bogstad, B., Dingsør, G. E., Gjøsæter, H., Ottersen, G., Eikeset, A. M., and
Stenseth, N. C. 2010. Trophic interactions affecting a key ecosystem component: a multistage analysis of the recruitment of the Barents Sea capelin. Canadian Journal of Fisheries
and Aquatic Science 67:1363-1375.
Røttingen, I. and Tjelmeland, S. 2011. The collapse of Norwegian spring-spawning herring
stock;
Climate or fishing? In IMR/PINRO joint report series 2/2011: Climate change and effects on the
Barents Sea marine living resources 15th Russian-Norwegian Symposium Longyearbyen,
7-8 September 2011, pp 217-224.
Skagseth, Ø., Furevik, T., Ingvaldsen, R., Loeng, H., Mork, K.A., Orvik, K.A., Ozhigin, V. (2008)
Volume and heat transports to the Arctic via the Norwegian and Barents Seas, pp. 45-64.
In Arctic-Subarctic Ocean Fluxes: Defining the role of the Northern Seas in Climate. Eds.
R. Dickson, J. Meincke and P. Rhines, Springer Netherlands, doi: 10.1007/978-1-4020-6774-7
3.13 Impact of climate variability on North Atlantic plankton
P. Licandro
An analysis of plankton time-series reveals that, in the North Atlantic, important
changes have occurred in the abundance, distribution, community structure, and
population dynamics of phytoplankton and zooplankton. The changes in the plankton appear to be responding to regional climate variability, caused predominately by
the warming of air and SSTs, and associated changes in hydrodynamics. Anthropogenic pressures (e.g. fishing) may also affect the community composition and abundance of plankton and may act synergistically with the climate. Changes in
phytoplankton and zooplankton communities at the bottom of the marine pelagic
food-web may affect higher trophic levels (e.g. fish, seabirds), because the synchrony
between predator and prey (match –mismatch) plays an important role (bottom – up
control of the marine pelagic environment) in the successful recruitment of top
predators, such as fish, seabirds, and mammals.
The poor recruitment of several fish species of commercial interest and the low seabird breeding productivity recorded in recent years in some North Atlantic regions
seem to be associated with changes in plankton biomass and in the seasonal timing of
plankton production (Figure 1).
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Figure 1. Partial residuals plots for the multiple regression of Sandeel Biomass Index (SBI) (1
May) against diatom (A) and copepod (B) records in the previous months (January–April). The
influence of sandeels on the recruitment of seabirds was tested over the period 1986–2003 comparing the first principal component of seabird productivity (Seabird PC1) versus the SBI index in
the previous year (C).
Figures reproduced from Frederiksen, M., Edwards, M., Richardson, A. J., Halliday, N. C., and
Wanless, S. 2006. From plankton to top predators: bottom–up control of a marine food web across
four trophic levels. Journal of Animal Ecology, 75: 1259–1268.
For further reading: Licandro P., Head, E., Gislason, A., Benfield, M.C., Harvey, M.,
Margonski, P., Slke, J. 2011. Overview of trends in plankton communities, pp. 103122. In: Reid, P. C., and Valdés, L. 2011. ICES status report on climate change in the
North Atlantic. ICES Cooperative Research Report No. 310. 262 pp.
3.14 Identifying drivers for zooplankton variability: the genetic programming
approach
A. Conversi and S. Marini
The issue of what drives zooplankton populations still eludes scientific investigations. In the last couples of decades, climate indices have become very popular, and
multiple correlations between these and the variations in zooplankton abundance/biomass have been identified. Still the issues remains, what indices, and why?
This choice of which indices is obviously very important. To this aim, the scientific
community has mainly used two approaches: using pressure-based, large scale indices (mostly NAO), or temperature based indices (such as NHT or AMO); (Drinkwater
et al., 2003; Conversi et al., 2010; Alheit et al., 2012). Or making area-specific indices
(e.g. Molinero et al., 2008).
The first approach has the convenience of using indices proposed by expert climatologists, with the added bonus of being easily downloadable from climate sites
(hence its widespread usage). However, these indices may not be appropriated for
basins far from the pressure centres. For example, the North Atlantic Oscillation
(NAO) index is not appropriate for the whole Mediterranean Sea, even if correlations
have been found with the physical circulation and with copepod species in the western basin (Rixen et al., 2005; Molinero et al., 2005). Other large scale atmospheric patterns, as for instance those related to the monsoon systems, may become more
prominent in the eastern basin (Raicich et al., 2003), and the choice of a climate index
that better synthesizes the influence of interannual to decadal climate variability in
such areas is still under debate. Moreover, there is also a more general problem with
NAO indices: since the 90s the centres of action of the NAO have moved east. In
other words, the usual NAO index, measured at Reykjavik and Azores, since the 90s
does not represent well the strength of the North Atlantic Oscillation.
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The second approach, building an area-specific index, has the advantage that the index can be centred on the area investigated. However, doing this requires a substantial collaboration between ecologists/physicists and climatologists in order to make a
meaningful index, which is no easy task. It also has the disadvantage of producing an
increasing number of indices, which may be confusing for the larger scientific audience.
Both these approaches usually rely on identifying significant correlations between the
indices and the marine populations, hence assume a linear behaviour. But ecosystems
often present abrupt jumps (regime shifts), or other non-linear behaviour. A different
approach needs to be used to capture this type of variability. An additional problem
with the previous approaches is that it does take into consideration synergistic effects, as each index is considered as a unique driver.
We have chosen a third way: that of not making assumptions at all, and are currently
investigating the use of Genetic Programming for identifying the drivers for zooplankton variability and possibly for predicting it. Genetic programming (GP) makes
no assumptions, neither on the drivers, nor on the type of relationship. Through multiple iterative procedures, mathematical ‘best fits’ of the variable under study are selected.
As a test case we have used the copepod time series measured at station L4 off the
Western Channel (Figure 1, red bars). A resulting approximation function is shown in
Figure 1 (blue bars).
As possible drivers we have chosen:
•
•
•
•
pressure-based climate variables, NAO, East Atlantic Pattern (EA), East
Atlantic West Russia Pattern (EAWR), Scandinavian Pattern (SCA), Polar
Eurasia Pattern (POL);
temperature based global/regional variables, Northern Hemisphere Temperature (NHT), Atlantic Multidecadal Oscillation (AMO);
local hydrographical variables, Sea Surface Temperature (sst), salinity (sal);
and local trophic variables, chlorophyll (chl), microzooplankton (mzp), total organic carbon (toc), total organic nitrogen (ton).
Figure 1. Copepod time series at station L4 (red) and approximation function derived from the
genetic programming (blue). From Marini and Conversi (2012).
Figure 2 shows the variables that have been identified as more ‘relevant’ for the approximation of the copepod series out of about 100 runs. The most relevant variables
belong to each group of drivers (pressure based climate indices, local hydrography,
and trophic parameters). However, they are not what one may expect: for example, it
appears that ‘trophic’ parameters (toc, ton), but not prey proxies (chlorophyll or microzooplankton), are more relevant than climate or temperature. Local temperature
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seems much more important than the hemispheric NHT. And EA seems much more
relevant than NAO.
Figure 2. Relevance of the environmental drivers based on three different types of approximation.
From Marini and Conversi (2012).
More details on the environmental variables used for the approximation of the copepod time series, on the GP approach used for this approximation, and on the three
sets of operators S1, S2 and S3, are given by Marini and Conversi (2012),
http://www.springerlink.com/content/l008166136683117.
Additional experiments on different basins will verify the validity of this approach.
References
Alheit, J., Pohlmann T, Casini M, Greve W, Hinrichs R, Mathis M, O'Driscoll K, Vorberg R,
Wagner C. 2012. Climate variability drives anchovies and sardines into the North and Baltic Seas. PROGRESS IN OCEANOGRAPHY: 96 (1): 128-139, ISSN: 0079-6611, DOI:
10.1016/j.pocean.2011.11.015.
Conversi, A., Fonda Umani S, Peluso T, Molinero JC, Santojanni A, Edwards M. 2010. The
Mediterranean Sea Regime Shift at the End of the 1980s, and Intriguing Parallelisms with
Other European Basins. PLoS ONE 5(5): e10633. doi:10.1371/journal.pone.0010633.
Drinkwater, K., A. Belgrano, A. Borja, A. Conversi, C. Greene, G. Ottersen, A. Pershing, (2003).
“The response of marine ecosystems to climate variability associated with the North Atlantic Oscillation”. In: The North Atlantic Oscillation: climatic significance and environmental impact, edited by J. Hurrell, Y. Kushnir, G. Ottersen, and M. Visbeck, American
Geophysical Union, Washington DC, Geophysical Monograph Series, Vol. 134, pp. 211234. ISBN 0-87590-994-9.
Marini, S., and Conversi A. 2012. Understanding zooplankton long term variability through
Genetic Programming. In: Evolutionary Computation, Machine Learning and Data Mining
in Bioinformatics. M. Giacobini, L. Vanneschi, and W.S. Bush (Eds.). Lecture Notes in
Computer Science Series, vol. 7246, pp. 50–61. , DOI: 10.1007/978-3-642-29066-4_5
Berlin
Heidelberg.
Springer-Verlag
http://www.springerlink.com/content/l008166136683117.
Molinero, J.C., Ibanez F, Nival P, Buecher E, Souissi S. 2005. The North Atlantic Climate and
northwestern Mediterranean plankton variability. Limnol Oceanogr 50: 1213–1220.
Molinero, J.C., Ibanez F, Souissi S, Buecher E, Dallot S, et al. 2008a. Climate control on the longterm anomalous changes of zooplankton communities in the northwestern Mediterranean.
Glob. Change Biol, 14: 11–26.
Raicich, F., N.Pinardi and A.Navarra. 2003. Teleconnections between Indian monsoon and Sahel rainfall and the Mediterranean. International Journal of Climatology 23:173-186.
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Rixen, M., Beckers JM, Levitus S, Antonov J, Boyer T, et al. 2005. The Western Mediterranean
Deep Water: A proxy for climate change.
Geophys Res Lett 32: L12608.
doi:10.1029/2005GL022702.
4
Results and intersessional activities
The discussion focused on the impact of the AMO on small pelagic fishes and their
ecosystems. As time was not sufficient to deliver corresponding results on all populations of small pelagics under investigation, it was decided to continue the work during the intersessional period and present the results in a peer-reviewed publication as
a contribution to a Special Issue on the AMO in the Journal of Marine Systems.
5
Elections, place and dates of the next meeting
Priscilla Licandro was elected as the co-chair for WGSPEC.
Because of logistical advantages it was decided to organize the 2013 meeting of
WGSPEC again at the Centro Oceanográfico de Málaga in Fuengirola, Spain, from 25
February to 1 March 2013.
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ICES WGSPEC REPORT 2012
Annex 1: List of participants
Jürgen Alheit
Leibniz Institute for
+49 3815197208 juergen.alheit@io-warnemuende.de
Baltic Sea Research
Seestr. 15
18119 Warnemünde, Germany
Piera Carpi
CNR-ISMAR
+39 3402705573
piera.carpi@an.ismar.cnr.it
+44(0)1752-584962
a.conversi@ismar.cnr.it
+34 93 230 95 00
costalago@icm.csic.es
Largo Fiera della Pesca, 2
60125, Ancona, Italy
Alessandra Conversi
SAHFOS
The Laboratory
Citadel Hill
PL1 2PB Plymouth, UK
David Costalago
Institut de Ciencies del Mar
CSIC
Passeig Maritim, 37-49
08003 Barcelona, Spain
Unai Cotano
AZTI Foundation
ucotano@azti.es
Herrera Kaiaz/g
20110 Pasaia
Gipuzkoa, Spain
Andrea De Felice
CNR-ISMAR
Largo Fiera della Pesca, 2
60125, Ancona, Italy
+39 0712078834
andrea.defelice@an.ismar.cnr.it
ICES WGSPEC REPORT 2012
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Lourdes Fernández-Peralta
Instituto Español de Oceanografía
+34 952197066 lourdes.fernandez@ma.ieo.es
Centro Oceanográfico de Málaga
Puerto Pesquero s/n
29640 Fuengirola, Spain
Alberto Garcia
Instituto Español de Oceanografía
+34 952197123 agarcia@ma.ieo.es
Centro Oceanográfico de Málaga
Puerto Pesquero s/n
29640 Fuengirola, Spain
Mª Teresa García Santamaria
Instituto Español de Oceanografía
+34922549400-01
teresa.garcia@ca.ieo.es
Calle General Gutiérrez, 4
38003 Santa Cruz de Tenerife, Spain
Eva García-Isarch
Instituto Español de Oceanografía
+34 956 294 189
eva.garcia@cd.ieo.es
Centro Oceanográfico de Cádiz
Muelle de Levante (Puerto Pesquero)
Apdo. 2609
11006 Cádiz, Spain
Susana Garrido
Universidade de Lisboa
+351 21 486 92 11
garridosus@gmail.com
Centro de Oceanografia
Avenida Nossa Sra. do Cabo, 939
2750-374 Cascais, Portugal
Ana Giráldez
Instituto Español de Oceanografía
Centro Oceanográfico de Málaga
Puerto Pesquero s/n
29640 Fuengirola, Spain
+34 952198073 agiraldez@ma.ieo.es
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ICES WGSPEC REPORT 2012
Rafael González-Quirós
Instituto Español de Oceanografía
+34 985309780 rgq@gi.ieo.es
Centro Oceanográfico de Gijón
Avenida Príncipe de Asturias, 70 bis
33212 Gijón, Spain
Åge Høines
Institute of Marine Research
+47 55 23 86 74
aage.hoines@imr.no
Nordnesgaten 50
5005 Bergen, Norway
Kathryn Hughes
National University of Ireland
+353 851310995
k.hughes4@nuigalway.ie
203 MRI Annexe
Martin Ryan Institute
University Road,
Galway, Ireland
Mª Paz Jiménez
Instituto Español de Oceanografía
+34 956 294 189 paz.jimenez@cd.ieo.es
Centro Oceanográfico de Cádiz
Muelle de Levante (Puerto Pesquero)
Apdo. 2609
11006 Cádiz, Spain
Priscilla Licandro
SAHFOS
+44 1752633133
prli@sahfos.ac.uk
The Laboratory
Citadel Hill
PL1 2PB Plymouth, UK
Elvira Morote
Centro de Ciências do Mar
Universidade do Algarve
Campus de Gambelas
8005-139 Faro, Portugal
+351 289800900 elvira.morote@yahoo.es
ICES WGSPEC REPORT 2012
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Isabel Palomera
Institut de Ciencies del Mar
+34 93230951192
palomera@icm.csic.es
CSIC
Passeig Maritim, 37-49
08003 Barcelona, Spain
Fernando Ramos
Instituto Español de Oceanografía
+34 956 294 189 fernando.ramos@cd.ieo.es
Centro Oceanográfico de Cádiz
Muelle de Levante (Puerto Pesquero)
Apdo. 2609
11006 Cádiz, Spain
Paulo Relvas
Universidade do Algarve
+351 289800900
Campus de Gambelas
ext: 7166
prelvas@ualg.pt
8005-139 Faro, Portugal
Miguel Santos
Instituto de Investigação das Pescas
+351 213027193
amsantos@ipimar.pt
Institute of Marine Research
+47 552384222
aril.slotte@imr.no
Nordnesgaten 50
etg 226
e do Mar (IPIMAR)
Av. de Brasília
1449-006 Lisboa, Portugal
Mike Sinclair
Bedford Institute of Oceanography
P.O. Box 1006
Dartmouth, NS, Canada
Aril Slotte
5005 Bergen, Norway
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ICES WGSPEC REPORT 2012
Athanassios Tsikliras
Department of Ichthyology
atsik@bio.auth.gr
and Aquatic Environment
University of Thessali
38446 Volos, Greece
Karl van Ginderdeuren
Institute for Agricultural
and Fisheries Research
Ankerstraat 1
8400 Oostende, Belgium
karlvanginderdeuren@ilvo.vlaanderen.be
ICES WGSPEC REPORT 2012
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Annex 2: Agenda
Monday, 27 February
10:30-10:40 Welcome
A. Garcia, J. Alheit, M. Sinclair
10:40-11:10 Small pelagic research framework in the Mediterranean
A. Garcia
11:10-11:
11:40-11:30 Coffee break
12:00-12:10 Vital rates of sardine and anchovy larvae determined in the laboratory
S. Garrido
12:10-12:30 Molecular characterization of the planktonic community diet in coastal
waters of the Alborán Sea: Sardina pilchardus larvae and its zooplanktonic preys
L. Yebra
12:30-13:30 Introduction to working group meeting
J. Alheit
13:30-15:00 Lunch break
15:30-16:30 Climate variability in northern hemisphere
J. Alheit
16:30-17:00 Long Term Variability of the Canary Current Upwelling System
P. Relvas
17:00-18:00 Mediterranean climate, circulation and zoopalnkton
A. Conversi
Tuesday, 28 February
09:00-09:50 Impact of climate variability on North Atlantic plankton
P. Licandro
09:50-10:20 Atlantic herring: explanation of spatial patterns of spawning
M. Sinclair
10:20-10:35 Spatial and temporal distribution of clupeids in the Belgian part of the
North Sea
K. van Ginderdeuren
10:35-10:50 Coffee break
11:00-10:30 Impact of climate variability on anchovies, sardines and sprat in North
and Baltic Seas
J. Alheit
11:30-12:10 Anchovy: environment, biology and recruitment in Bay of Biscay
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ICES WGSPEC REPORT 2012
U. Cotano
12:10-12:40 Long-term variability of small pelagics and relationships with environment
R. González-Quirós
12:40-13:30 Decadal changes in sardines and anchovies in the Canary Current Upwelling System
M. Santos
15:40-16:30 An overview of large and mesoscale oceanographic processes relevant to
the Gulf of Cádiz anchovy
F. Ramos
16:30-17:00 Historical landings of small pelagics off NW Africa (Spanish fisheries).
Signals of the climatic effect on small pelagic in the Canary Islands
M.T. García Santamaría and E. García Isarch
17:00-17:40 Environmental impacts on anchovy, sardine and sardinella in the northwestern Mediterranean
I. Palomera
17:40-18:00 Insights into the trophic dynamics of juveniles of anchovy and sardine in
the NW Mediterranean and how climate change can affect it
D. Costalago
Wednesday, 29 February
09:10-09:40 Biomass evaluation of anchovy (E. encrasicolus), sardine (S. pilchardus)
and sprat (S. sprattus) in the western Adriatic Sea by means of acoustics and preliminary analysis of possible relationships with environmental parameters
A. de Felice
09:50-10:10 Population dynamics of small pelagic species in the Adriatic Sea: stock
assessment models and environmental factors
P. Carpi
10:10-10:30 Impact of climate variability on anchovies, sardines, sprat in Adriatic Sea
A. Conversi
10:30-11:10 Impact of climate variability on small pelagic fishes in eastern Mediterranean
A. Tsikliras
11:10-11:40 Coffee break
11:40-12:10 NAO related small pelagic fisheries fluctuations off Morocco and Senegal
L. Fernández-Peralta
12:10-13:00 Impact of climate variability on herring and capelin in northern seas
A. Slotte
13:00-15:00 Lunch break
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15:00-15:40 Changes in the location and extent of North East Atlantic mackerel
catches: possible fishery and climate change effects
K. Hughes
15:40-16.00
16:00-16:40 Impact of Atlantic Multidecadal Oscillation on small pelagics in NE Atlantic
J. Alheit
16:40-17:00 Coffee break
17:00-18:00 Comparison of data and statistical analysis
Thursday, 1 March
09:00-13:00 Comparison of data and statistical analysis (ctd.)
13:00-14:30 Lunch break
14:30-16:00 Comparison of data and statistical analysis (ctd.)
16:00-16:30 Coffee break
16:30-17:00 Report
17:00-18:00 Comparison of data and statistical analysis (ctd.)
Friday, 2 March
09:00-11:00 Presentation of results
11:00-11:30 Coffee break
11:30-13:00 Discussion of future activities of Working Group
Date and place of 2013 meeting
Election of co-chair
13:00
End of meeting
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ICES WGSPEC REPORT 2012
Annex 3: Draft terms of reference for the next meeting
a ) Presentation and discussion of statistical analyses carried out during intersessional period;
b ) Specific analysis of climate impact and respective physical and biological
processes around the mid-1990s;
c ) Study mechanisms that link the variability of the small pelagic fish populations in different ocean basins to the large scale climatic forcings;
d ) Suggest relevant joint theme sessions and workshops for ICES and PICES
which are also relevant to ICES assessment working groups on pelagic
fish;
e ) Prepare contributions for the 2012 SSGEF session during the ASC on the
topic areas of the Science.
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Annex 4: Cycles, trends, and residual variation in the Iberian sardine
( Sardina pilchardus) recruitment series and their relationship with
the environment
R. González-Quirós
Recruitment variability is an important component of the dynamics of Iberian sardine
(Sardine pilchardus). Since 2006, poor recruitment has led to a decrease in stock biomass, the latest in a series of such crises for sardine fisheries. Understanding the
mechanisms behind recruitment fluctuations has been the objective of many previous
studies, and various relationships between recruitment and environmental variables
have been proposed. However, such studies face several analytical challenges, including short time-series and autocorrelated data. A new analysis of empirical relationships with environmental series is presented, using statistical methods designed
to cope with these issues, including dynamic factor analysis, generalized additive
models, and mixed models.
Relationships are identified between recruitment and global (number of sunspots),
regional (NAOAutumn), and local [winter wind strength, sea surface temperature
(SST), and upwelling] environmental variables. Separating these series into trend and
noise components permitted further investigation of the nature of the relationships.
Whereas the other three environmental variables were related to the trend in recruitment, SST was related to residual variation around the trend, providing stronger
evidence for a causal link, possible mechanisms for which are discussed. After the
removal of trend and cyclic components, residual variation in recruitment is also
weakly related to the previous year’s spawning-stock biomass.
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ICES WGSPEC REPORT 2012
Annex 5: Small pelagic fishes and zooplankton in Belgian waters
K. van Ginderdeuren
In the Belgian Part of the North Sea, pelagic fish and zooplankton data are gathered
by taking monthly samples with a (semi-)pelagic trawl (4*4m opening) and a WP2
(200µm) net. Herring Clupea harengus and sprat Sprattus sprattus are common in the
BPNS but are rarely found in high numbers. Most fish belong to the 0- and 1-year
cohorts and are mainly found near the shore. Adult herring are present in autumn,
when large schools migrate through the BPNS on their way to the spawning grounds
in the French Channel. Spring and summer bring along two other pelagic key species:
mackerel Scomber scombrus and horse mackerel Trachurus trachurus. The latter reproduces in the BPNS and its larvae are very abundant, but also larvae of herring, sprat
and sardine Sardina pilchardus are found in high numbers. Rarer catches included
adult sardine, anchovy Engraulus encrasicolus and one blue whiting Micromesistius
poutassou.
Preliminary analyses of the zooplankton point out that calanoid copepods are the
dominant holoplanktonic fauna in the water column, with Temora longicornis, Acartia
clausi, Paracalanus parvus, Centropages typicus and C. hamatus as most abundant species. Further offshore more oceanic species such as Calanus helgolandicus occur. In addition, meroplanktonic organisms such as larvae of polychaetes, echinoderms and
barnacles are very common. Also, high densities of the invasive jellyfish Mnemiopsis
leidyi are found in the plankton hauls during summer and autumn.
More knowledge concerning the spatial and temporal variation in zooplankton
abundance, in relation to the presence of pelagic fish and their feeding ecology is crucial to assess the importance of the zooplankton as a fish food source. Stomach content analyses are carried out for herring, sprat, horse mackerel and mackerel to
investigate the spatial and temporal variation in their diet (see figure for preliminary
analysis).
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Herring
Sprat
Mackerel
Horse mackerel
Sprat is feeding almost exclusively on calanoid copepods, whilst herring often targets
bigger prey items. This is also the case for juvenile herring the size of adult sprat.
Mackerel stomachs sometimes contain fish in addition to plankton (mostly sandeels).
Horse mackerel apparently forages closer to the bottom, resulting in polychaetes and
bivalve spat being present in the stomach content.
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Annex 6: Vital rates of pelagic fish larvae (VITAL)
S. Garrido
Laboratory experiments are being carried out as part of the project VITAL, financed
by the Portuguese Foundation for Science and Technology (PTDC/MAR/111304/2009;
http://projectvital.fc.ul.pt) with the objective of studying the vital rates of sardine
(Sardina pilchardus) and anchovy (Engraulis encrasicolus) larvae in relation to differences in several key physical and biological factors considered most important for
regulating their growth and survival. The experiments aim at obtaining parameters
such as 1) the upper and lower physiological tolerance limits of temperature, salinity
and food availability for larvae survival and their influence on larvae growth; 2) the
ingestion rates of different prey types offered at different concentrations and at different temperatures and salinities, simulating field values. The nutritional condition
of larvae reared in the laboratory are being monitored and compared with larvae collected in the wild, validating combined techniques (fatty acids and RNA/DNA). The
quantitative estimates of the vital rates for the larvae of these fish species under controlled laboratory conditions will be used to parameterize an individual-based model
to be coupled to a hydrodynamic model developed for the western Portuguese coast
(Project MODELA PTDC/MAR/098643/2008). Efforts to build models describing environmental regulation of these species in other systems around the world (e.g. to examine links between climate and recruitment) are currently hampered by a lack of
data, namely of the vital rates of the vulnerable larval phase, that we hope to contribute with our research.
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Annex 7: Changes in the location and extent of North East Atlantic
mackerel catches: possible fishery and climate change effects
K. Hughes, M. Johnson, L. Dransfield
Widely available fisheries data is often ignored for fisheries research due to the complex nature of identifying anthropogenic from environmental signals. This research
aims to use the north east Atlantic mackerel (Scomber scombrus) vessel log book data
to identify and further investigate patterns from potential fisheries and environmental effects. The data were analysed by quarter using an EOF to identify locations
of highest variability. Initial analysis of quarter one showed a strong increasing and
decreasing signal around the Cornish peninsula of England around the time of the
early 1980s. This pattern corresponded to the closure of the south west mackerel box
from trawlers in the spring, summer and autumn months. Since the mid-1980s the
mackerel fishery in this region is almost exclusively from handlines. The result supports the usefulness of an EOF as an effective method for depicting patterns in the
data. Since we can be relatively confident the signal we were seeing was due to
known fisheries legislation, the area of the SWMB was removed to test for other spatial patterns of variance in the data. In quarter one, an on shelf off shelf movement
appears around the early 1980s, possibly a climate driven effect moving the spawning
stock off shelf, alternatively a cohort effect may be influencing the fishery towards
more off shelf areas whilst the overall distribution remains the same. In quarter two
the catch is highly variable with large catches in sporadic positions north and west.
There is a large catch in the International waters of the southern Norwegian Sea,
probably due to fisheries area TACs. There is a general increase in catch in more
northern areas along the continental shelf edge, possibly as a result of warming seas.
In quarter three there are probable fishing effects between coastal Norway and International waters in the southern Norwegian Sea, with PC2 picking up an increase in
catch in the southern Norwegian Sea from the mid-1990s. Highly variable catches are
taken in coastal areas and in the North Sea. Quarter four showed an east-west
movement in the early nineties which could be a fishing effect from closed areas and
subsequent misreporting between ICES areas IVa and VIa. Future research will characterise each location by SST, Chla, Calanus finmarchicus abundance and bottom depth
to address the different trends in the data and attempt to discern environmental from
fisheries drivers.