The determination of reproductive status and the reconstruction of individual reproductive histor... more The determination of reproductive status and the reconstruction of individual reproductive histories are central to many ecological studies. In cetaceans, it has been assumed that ovarian scars accumulate with age and provide a lifetime record of female reproductive history. If ovarian scars persist, the number of scars should increase with age after puberty. To test this, we examined age, reproductive status and ovarian scars from 187 short-beaked common dolphins (Delphinus delphis) from the eastern North Atlantic. The number of Corpus Albicans (CA) present in ovaries did not increase with age after age at sexual maturity (ASM), suggesting that ovarian scars are not persistent and that their number at any one time would be a function of rates of ovulation and healing, the latter being defined here as the resorption or disintegration of CA tissue. Since female mammals stop ovulating when pregnant, inferences about healing rates could be made by using pregnant females. Pregnant females had ca. 40% fewer scars than non-pregnant females. This suggests that most CAs would heal quickly, with a half-life of less than 1 year, although larger scars may persist longer. Therefore, counting CAs would have limited potential for reconstructing individual reproductive lifetime histories in the common dolphin. A reassessment of the use of ovarian scars to reconstruct individual life reproductive histories in cetaceans is suggested.
Journal of Experimental Marine Biology and Ecology, 2010
Defining trophic relationships among organisms of a community is critical in ecology. However, th... more Defining trophic relationships among organisms of a community is critical in ecology. However, the access to data is sometimes difficult, particularly in remote environments. Ecological niche segregation among the most common delphinid species was investigated: the spinner dolphin (Stenella longirostris), the roughed-toothed dolphin (Steno bredanensis), the short-finned pilot whale (Globicephala macrorhynchus), and the melon-headed whale (Peponocephala electra). Resource partitioning was explored by analysing δ13C (reflecting foraging habitats) and δ15N stable isotopes (reflecting trophic level) from skin biopsies collected around Moorea from July to October 2002 to 2004. Results revealed that spinner dolphins had the lowest trophic level. The three other species had similar δ15N signatures. The most significant result is the differentiation of S. longirostris from S. bredanensis and G. macrorhynchus but not from the P. electra. For the latter three species, some degrees of overlap were apparent. For S. longirostris, S. bredanensis and G. macrorhynchus, variation of δ13C and δ15N stable isotope was not significant between sexes. This study suggests that stable isotopes reveal some degree of segregation and overlap within this delphinid community. However, fine-scale segregation processes may be concealed by stable isotope analyses, meaning that traditional dietary analyses investigations are complementary in answering questions related to niche segregation.
The CETA program (Distribution des cétacés en Terre Adélie) was launched by the French Polar Inst... more The CETA program (Distribution des cétacés en Terre Adélie) was launched by the French Polar Institute (IPEV) in 2009 to carry out a first pilot study on cetacean distribution off Adelie Land (IWC Area V). An opportunistic survey conducted in January 2010 allowed the collection of 38 sightings on the continental shelf off the Adélie Land coastline, totalising a minimum of 84 individuals. True blue whales ( Balaenoptera musculus ) and humpback whales ( Megaptera novaeangliae ) were identified for the first time in the Adélie Land region. Sightings of antarctic minke whale ( Balaenoptera bonaerensis ) and killer whale ( Orcinus orca ) type A and C confirmed the presence of both species in this area. Photo-ID were realised on three blue whales and two humpback whales. One of the two humpback was previously photo-ID in Hervey Bay, East Australia in 2002. A biopsy was collected on one humpback whale. The presence of great whales (8 individuals of blue and humpback whales) in the Adélie Depression raised the issue of the importance of this area for such endangered species. The second year of this pilot study will be conducted in January 2011, after which data will combined to evaluate relative abundance of cetaceans in the region. This work is a part of the Southern Ocean Research Partnerships (SORP) on non-lethal whale research.
... This short communication describes a case of a double-faced monster in a bottlenosed dolphin ... more ... This short communication describes a case of a double-faced monster in a bottlenosed dolphin (Tursiops truncatus) found stranded on the French Mediterranean ... The malformation mostly affected the face of the animal and to a lesser extent the brain case (Figs 1, 2). The skull ...
We describe the structure of a toothed cetacean community around the island of Mayotte (South-Wes... more We describe the structure of a toothed cetacean community around the island of Mayotte (South-West Indian Ocean, 45°10′ E, 12°50′ S), using data collected from small boat-based surveys conducted between July 2004 and June 2006. In all, 16 odontocete species were recorded. Diversity (Shannon-Weaver index) was particularly high along the outer slope of the barrier reef. Patterns of spatial distribution underscore the existence of three main cetacean habitat types: the inner lagoon (Indo-Pacific bottlenosed dolphin Tursiops aduncus and humpback dolphin Sousa chinensis), the outer-reef slope (spinner dolphin Stenella longirostris, pantropical spotted dolphin S. attenuate and melon-headed whale Peponocephala electra) and oceanic waters deeper than 500 m (e.g. Blainville's beaked whale Mesoplodon densirostris). Group characteristics were highly variable among species, with oceanic small delphinids characterised by larger group sizes than strictly coastal and non-delphinid oceanic species. The outer slope of the barrier reef appears to be of primary importance in terms of density and diversity of odontocetes around Mayotte. Results support the hypothesis that a number of cetacean species, particularly several delphinid species, are dependent on coral reef complexes.
In order to establish a baseline map of cetaceans a nd other pelagic megafauna across the French ... more In order to establish a baseline map of cetaceans a nd other pelagic megafauna across the French EEZ (Figure 1), the French agency for marine protected areas (AAMP) decided to conduct a series of surveys allowing hotspots of a bundance and diversity to be identified and a future monitoring scheme to be established. This paper describes the general desig n,
Journal of Northwest Atlantic Fishery Science, 2010
As top predators, marine mammals can provide information on the accumulation of anthropogenic tox... more As top predators, marine mammals can provide information on the accumulation of anthropogenic toxins which present the greatest risk to consumers. We assessed the impacts of persistent organic pollutants (POPs) on two cetacean species that feed on commercially important fi sh species in the eastern North Atlantic; the common dolphin (Delphinus delphis) and the harbour porpoise (Phocoena phocoena). In order to evaluate the possible long-term effects of POPs on the continued viability of these populations, we investigated their effects on reproductive activity in females, using ovarian scars as an index of reproductive activity. In harbour porpoises, high POP burdens tended to be associated with lower ovarian scar number, possibly indicating that high contaminant levels were inhibiting ovulation, or some females may go through a number of infertile ovulations prior to a successful pregnancy, birth, and survival of their fi rst offspring during early lactation. In contrast, initial results identifi ed that the common dolphins with contaminant burdens above a threshold level for adverse health effects in marine mammals (17 μg g -1 total PCBs lipid) were resting mature females, with *Corresponding Author 154 high numbers of ovarian scars. This suggests that (a) due to high contaminant burdens, females may be unable to reproduce, thus continue ovulating, or (b) females are not reproducing for some other reason, either physical or social, and started accumulating higher levels of contaminants. Additional analyses were carried out on a control group of ''healthy'' D. delphis, i.e. stranded animals diagnosed as bycatch and were assessed for evidence of any infectious or non infectious disease that would inhibit reproduction. Results suggested that high contaminant burdens, above the threshold level, were not inhibiting ovulation, conception or implantation in female D. delphis, though the impact on the foetal survival rate (in both species) requires further examination. Investigations into accumulation and persistence of ovarian scars and use as an index of reproductive activity were also undertaken within this study.
Knowledge of relationships between predator size and prey size are needed to describe interaction... more Knowledge of relationships between predator size and prey size are needed to describe interactions of species and size classes in food webs. Most estimates of predator and prey sizes have been based on dietary studies and apply to small numbers of species in a relatively narrow size range. These estimates may or may not be representative of values for other groups of species and body sizes or for other locations. Marine predator and prey size data associated with published literature were identified and collated to produce a single data set. If predator or prey length of mass were not measured in the original study, the length or mass was calculated using length-mass relationships. The data set consists of 34 931 records from 27 locations covering a wide range of environmental conditions from the tropics to the poles and for 93 types of predator with sizes ranging from 0.1 mg to over 415 kg and 174 prey types with sizes from 75 pg to over 4.5 kg. Each record includes: predator and prey scientific names, common names, taxa, life stages and sizes (length and mass with conversion details), plus the type of feeding interaction, geographic location (with habitat description, latitude, longitude) and mean annual environmental data (sea surface temperature and primary productivity).
Located at 50°30' S, Madre de Dios archipelago is an outstanding natural and archeological herita... more Located at 50°30' S, Madre de Dios archipelago is an outstanding natural and archeological heritage, which Chile designated a protected area in January 2008. Together with Diego de Almagro Island (51°30'S), this is the most southerly and inhospitable karst on Earth, owing to a subpolar climate with extreme rainfall (>7-8 meters/year) and strong winds ("roaring fifties"). The Upper Carboniferous and Lower Permian Tarlton Limestones (500 m thick) form part of the pre-Jurassic basement of the Andean Cordillera, the former Pacific margin of Gondwana. Along the fjords and Pacific front, cliff-side exploration with rubber dinghies has revealed three exceptional caves with: 1) archeological artifacts (Pacific Cave); 2) glacial sediments (Moraine Cave); 3) stepped beaches and whale bones (Whale Cave).
Journal of Experimental Marine Biology and Ecology, 2010
Which characteristics define the prey species constituting the diet of a given predator? Answerin... more Which characteristics define the prey species constituting the diet of a given predator? Answering this question would help predict a predator's diet and improve our understanding of how an ecosystem functions. The aim of this study was to test if the diet of common dolphins, Delphinus delphis, in the oceanic Bay of Biscay reflected prey availability or a selection shaped by prey energy densities (ED). To do this, the community of potential prey species, described both in terms of relative abundance and energy densities, was compared to the common dolphin diet in this area. This analysis of a predator's diet and its prey field revealed that the common dolphin selected its diet on the basis of prey energy densities (significant values of Chesson's index for ED > 5 kJ g− 1). High-energy prey were positively selected in the diet [e.g. Notoscopelus kroeyeri, ED = 7.9 kJ g− 1, 9% of relative abundance in the environment (%Ne); 62% of relative abundance in the diet (%Nd)] and low-energy prey disregarded (Xenodermichthys copei, ED = 2.1 kJ g−1, 20%Ne, 0%Nd). These results supported the hypothesis that common dolphins selected high energy density prey species to meet their energetically expensive life style and disregard prey organisms of poor energy content even when abundant in the environment.
Deep-sea Research Part I-oceanographic Research Papers, 2011
Long-finned pilot whales (Globicephala melas), Risso's dolphins (Grampus griseus), melon-headed w... more Long-finned pilot whales (Globicephala melas), Risso's dolphins (Grampus griseus), melon-headed whales (Peponocephala electra), Cuvier's beaked whales (Ziphius cavirostris), Sowerby's beaked whales (Mesoplodon bidens), northern bottlenose whales (Hyperoodon ampullatus), sperm whales (Physeter macrocephalus), dwarf sperm whales (Kogia sima) and pygmy sperm whales (Kogia breviceps) make up the large community of deep-diving odontocetes occurring off the Bay of Biscay, northeast Atlantic. The ecology of these toothed cetaceans is poorly documented worldwide. The present study described their prey preferences from stomach content analysis and showed resource partitioning within the assemblage. The majority of the species appeared to be mostly teutophageous. Fish was an important food source only for the Sowerby's beaked whale and, to a lesser extent, for the long-finned pilot whale. In terms of foraging habitats inferred from prey composition, either pelagic oceanic or demersal neritic habitats were exploited by toothed whales in the Bay of Biscay, with only the long-finned pilot whale foraging in the two habitats. Finally, with more than 14,000 identified cephalopods from 39 species, the present study highlighted also the poorly known deep-sea cephalopod community off the Bay of Biscay using top predators as biological samplers.► New insights in the foraging ecology of poorly documented deep-diving odontocetes. ► Successful example of food segregation within a top predator community. ► First study using biological samplers on deep-sea cephalopod fauna living in the northern Atlantic.
We investigated the status of the grey seal in the Molène archipelago, western Brittany, where a ... more We investigated the status of the grey seal in the Molène archipelago, western Brittany, where a Marine National Park is planned. We combined regular censuses, photo-identification and satellite telemetry to investigate trends in grey seal abundance, site fidelity, individual movements and haulout site use. Individual movements and seasonal variations in abundance suggest that the seals used the Molène archipelago alternatively with other haulout sites of the South-west British Isles during their annual cycle. Nine out of 16 seals fitted with Satellite Relay Data Loggers (SRDLs) moved to the Isles of Scilly, English Cornwall, Wales or the Channel islands. On average the seals spent 85% of their time Near Haulout, 56.8% of which in the Molène archipelago. Overall the seals spent 66% of their tracking time within the boundaries of the Marine National Park. From 1997 to 2000 in the Molène archipelago, we observed a peak in number during the moulting season (mean = 49.8 seals) and a lower abundance during the breeding season (mean = 38.3 seals). The sex ratio was strongly skewed towards males during the moult (between 3.1 and 5.3–1), and was close to 1:1 during the summer. Inter-annual site fidelity outside the breeding season was very high, varying from 70% to 95% of identified seals, suggesting that the observed movements constitute rotations rather than random dispersion. From 1991/1994 to 1997/2000, the mean number of seals counted at haulout sites increased by 7%, close to the rates of increase observed in the core population of the British Isles at the same period. The Marine National Park may be too restricted for the overall conservation of the population but management plans should be aimed at preserving the characteristics of the habitat for the grey seal.
As part of a larger project on the feeding ecology of large pelagic predators off the Bay of Bisc... more As part of a larger project on the feeding ecology of large pelagic predators off the Bay of Biscay, this study analyses the diet of the swordfish, Xiphias gladius. Stomachs were collected from 86 swordfish. The diet was analysed in terms of prey occurrence, relative abundance, reconstituted mass, and size distribution. It consisted mainly of fish, 40.5% by mass (%M) and cephalopods, 59.3%M; crustaceans, 0.2%M, were considered secondary prey. When considering only the fresh fraction to allow for differential digestion rates, these figures were 77.3%M, 22.7%M, and trace amounts, respectively. Lanternfish, including Notoscopelus kroeyeri and Symbolophorus veranyi, were abundant, but paralepidids, Atlantic pomfret (Brama brama), and the squid Todarodes sagittatus, Ommastrephes bartramii, and Gonatus steenstrupi, dominated the diet by mass. The overall prey size range was 11e1420 mm, but sizes of 60e360 mm accounted for 80% of the distribution by number and of 140e760 mm for 80% of the distribution by mass. Intraspecifically, larger swordfish ate larger prey as a result of a change in species composition of the diet. The swordfish appears to show feeding plasticity both between different areas and between animals in the same area.
Spitz, J., Mourocq, E., Schoen, V., and Ridoux, V. 2010. Proximate composition and energy content... more Spitz, J., Mourocq, E., Schoen, V., and Ridoux, V. 2010. Proximate composition and energy content of forage species from the Bay of Biscay: high-or low-quality food? -ICES Journal of Marine Science, 67: 909 -915.
The determination of reproductive status and the reconstruction of individual reproductive histor... more The determination of reproductive status and the reconstruction of individual reproductive histories are central to many ecological studies. In cetaceans, it has been assumed that ovarian scars accumulate with age and provide a lifetime record of female reproductive history. If ovarian scars persist, the number of scars should increase with age after puberty. To test this, we examined age, reproductive status and ovarian scars from 187 short-beaked common dolphins (Delphinus delphis) from the eastern North Atlantic. The number of Corpus Albicans (CA) present in ovaries did not increase with age after age at sexual maturity (ASM), suggesting that ovarian scars are not persistent and that their number at any one time would be a function of rates of ovulation and healing, the latter being defined here as the resorption or disintegration of CA tissue. Since female mammals stop ovulating when pregnant, inferences about healing rates could be made by using pregnant females. Pregnant females had ca. 40% fewer scars than non-pregnant females. This suggests that most CAs would heal quickly, with a half-life of less than 1 year, although larger scars may persist longer. Therefore, counting CAs would have limited potential for reconstructing individual reproductive lifetime histories in the common dolphin. A reassessment of the use of ovarian scars to reconstruct individual life reproductive histories in cetaceans is suggested.
Journal of Experimental Marine Biology and Ecology, 2010
Defining trophic relationships among organisms of a community is critical in ecology. However, th... more Defining trophic relationships among organisms of a community is critical in ecology. However, the access to data is sometimes difficult, particularly in remote environments. Ecological niche segregation among the most common delphinid species was investigated: the spinner dolphin (Stenella longirostris), the roughed-toothed dolphin (Steno bredanensis), the short-finned pilot whale (Globicephala macrorhynchus), and the melon-headed whale (Peponocephala electra). Resource partitioning was explored by analysing δ13C (reflecting foraging habitats) and δ15N stable isotopes (reflecting trophic level) from skin biopsies collected around Moorea from July to October 2002 to 2004. Results revealed that spinner dolphins had the lowest trophic level. The three other species had similar δ15N signatures. The most significant result is the differentiation of S. longirostris from S. bredanensis and G. macrorhynchus but not from the P. electra. For the latter three species, some degrees of overlap were apparent. For S. longirostris, S. bredanensis and G. macrorhynchus, variation of δ13C and δ15N stable isotope was not significant between sexes. This study suggests that stable isotopes reveal some degree of segregation and overlap within this delphinid community. However, fine-scale segregation processes may be concealed by stable isotope analyses, meaning that traditional dietary analyses investigations are complementary in answering questions related to niche segregation.
The CETA program (Distribution des cétacés en Terre Adélie) was launched by the French Polar Inst... more The CETA program (Distribution des cétacés en Terre Adélie) was launched by the French Polar Institute (IPEV) in 2009 to carry out a first pilot study on cetacean distribution off Adelie Land (IWC Area V). An opportunistic survey conducted in January 2010 allowed the collection of 38 sightings on the continental shelf off the Adélie Land coastline, totalising a minimum of 84 individuals. True blue whales ( Balaenoptera musculus ) and humpback whales ( Megaptera novaeangliae ) were identified for the first time in the Adélie Land region. Sightings of antarctic minke whale ( Balaenoptera bonaerensis ) and killer whale ( Orcinus orca ) type A and C confirmed the presence of both species in this area. Photo-ID were realised on three blue whales and two humpback whales. One of the two humpback was previously photo-ID in Hervey Bay, East Australia in 2002. A biopsy was collected on one humpback whale. The presence of great whales (8 individuals of blue and humpback whales) in the Adélie Depression raised the issue of the importance of this area for such endangered species. The second year of this pilot study will be conducted in January 2011, after which data will combined to evaluate relative abundance of cetaceans in the region. This work is a part of the Southern Ocean Research Partnerships (SORP) on non-lethal whale research.
... This short communication describes a case of a double-faced monster in a bottlenosed dolphin ... more ... This short communication describes a case of a double-faced monster in a bottlenosed dolphin (Tursiops truncatus) found stranded on the French Mediterranean ... The malformation mostly affected the face of the animal and to a lesser extent the brain case (Figs 1, 2). The skull ...
We describe the structure of a toothed cetacean community around the island of Mayotte (South-Wes... more We describe the structure of a toothed cetacean community around the island of Mayotte (South-West Indian Ocean, 45°10′ E, 12°50′ S), using data collected from small boat-based surveys conducted between July 2004 and June 2006. In all, 16 odontocete species were recorded. Diversity (Shannon-Weaver index) was particularly high along the outer slope of the barrier reef. Patterns of spatial distribution underscore the existence of three main cetacean habitat types: the inner lagoon (Indo-Pacific bottlenosed dolphin Tursiops aduncus and humpback dolphin Sousa chinensis), the outer-reef slope (spinner dolphin Stenella longirostris, pantropical spotted dolphin S. attenuate and melon-headed whale Peponocephala electra) and oceanic waters deeper than 500 m (e.g. Blainville's beaked whale Mesoplodon densirostris). Group characteristics were highly variable among species, with oceanic small delphinids characterised by larger group sizes than strictly coastal and non-delphinid oceanic species. The outer slope of the barrier reef appears to be of primary importance in terms of density and diversity of odontocetes around Mayotte. Results support the hypothesis that a number of cetacean species, particularly several delphinid species, are dependent on coral reef complexes.
In order to establish a baseline map of cetaceans a nd other pelagic megafauna across the French ... more In order to establish a baseline map of cetaceans a nd other pelagic megafauna across the French EEZ (Figure 1), the French agency for marine protected areas (AAMP) decided to conduct a series of surveys allowing hotspots of a bundance and diversity to be identified and a future monitoring scheme to be established. This paper describes the general desig n,
Journal of Northwest Atlantic Fishery Science, 2010
As top predators, marine mammals can provide information on the accumulation of anthropogenic tox... more As top predators, marine mammals can provide information on the accumulation of anthropogenic toxins which present the greatest risk to consumers. We assessed the impacts of persistent organic pollutants (POPs) on two cetacean species that feed on commercially important fi sh species in the eastern North Atlantic; the common dolphin (Delphinus delphis) and the harbour porpoise (Phocoena phocoena). In order to evaluate the possible long-term effects of POPs on the continued viability of these populations, we investigated their effects on reproductive activity in females, using ovarian scars as an index of reproductive activity. In harbour porpoises, high POP burdens tended to be associated with lower ovarian scar number, possibly indicating that high contaminant levels were inhibiting ovulation, or some females may go through a number of infertile ovulations prior to a successful pregnancy, birth, and survival of their fi rst offspring during early lactation. In contrast, initial results identifi ed that the common dolphins with contaminant burdens above a threshold level for adverse health effects in marine mammals (17 μg g -1 total PCBs lipid) were resting mature females, with *Corresponding Author 154 high numbers of ovarian scars. This suggests that (a) due to high contaminant burdens, females may be unable to reproduce, thus continue ovulating, or (b) females are not reproducing for some other reason, either physical or social, and started accumulating higher levels of contaminants. Additional analyses were carried out on a control group of ''healthy'' D. delphis, i.e. stranded animals diagnosed as bycatch and were assessed for evidence of any infectious or non infectious disease that would inhibit reproduction. Results suggested that high contaminant burdens, above the threshold level, were not inhibiting ovulation, conception or implantation in female D. delphis, though the impact on the foetal survival rate (in both species) requires further examination. Investigations into accumulation and persistence of ovarian scars and use as an index of reproductive activity were also undertaken within this study.
Knowledge of relationships between predator size and prey size are needed to describe interaction... more Knowledge of relationships between predator size and prey size are needed to describe interactions of species and size classes in food webs. Most estimates of predator and prey sizes have been based on dietary studies and apply to small numbers of species in a relatively narrow size range. These estimates may or may not be representative of values for other groups of species and body sizes or for other locations. Marine predator and prey size data associated with published literature were identified and collated to produce a single data set. If predator or prey length of mass were not measured in the original study, the length or mass was calculated using length-mass relationships. The data set consists of 34 931 records from 27 locations covering a wide range of environmental conditions from the tropics to the poles and for 93 types of predator with sizes ranging from 0.1 mg to over 415 kg and 174 prey types with sizes from 75 pg to over 4.5 kg. Each record includes: predator and prey scientific names, common names, taxa, life stages and sizes (length and mass with conversion details), plus the type of feeding interaction, geographic location (with habitat description, latitude, longitude) and mean annual environmental data (sea surface temperature and primary productivity).
Located at 50°30' S, Madre de Dios archipelago is an outstanding natural and archeological herita... more Located at 50°30' S, Madre de Dios archipelago is an outstanding natural and archeological heritage, which Chile designated a protected area in January 2008. Together with Diego de Almagro Island (51°30'S), this is the most southerly and inhospitable karst on Earth, owing to a subpolar climate with extreme rainfall (>7-8 meters/year) and strong winds ("roaring fifties"). The Upper Carboniferous and Lower Permian Tarlton Limestones (500 m thick) form part of the pre-Jurassic basement of the Andean Cordillera, the former Pacific margin of Gondwana. Along the fjords and Pacific front, cliff-side exploration with rubber dinghies has revealed three exceptional caves with: 1) archeological artifacts (Pacific Cave); 2) glacial sediments (Moraine Cave); 3) stepped beaches and whale bones (Whale Cave).
Journal of Experimental Marine Biology and Ecology, 2010
Which characteristics define the prey species constituting the diet of a given predator? Answerin... more Which characteristics define the prey species constituting the diet of a given predator? Answering this question would help predict a predator's diet and improve our understanding of how an ecosystem functions. The aim of this study was to test if the diet of common dolphins, Delphinus delphis, in the oceanic Bay of Biscay reflected prey availability or a selection shaped by prey energy densities (ED). To do this, the community of potential prey species, described both in terms of relative abundance and energy densities, was compared to the common dolphin diet in this area. This analysis of a predator's diet and its prey field revealed that the common dolphin selected its diet on the basis of prey energy densities (significant values of Chesson's index for ED > 5 kJ g− 1). High-energy prey were positively selected in the diet [e.g. Notoscopelus kroeyeri, ED = 7.9 kJ g− 1, 9% of relative abundance in the environment (%Ne); 62% of relative abundance in the diet (%Nd)] and low-energy prey disregarded (Xenodermichthys copei, ED = 2.1 kJ g−1, 20%Ne, 0%Nd). These results supported the hypothesis that common dolphins selected high energy density prey species to meet their energetically expensive life style and disregard prey organisms of poor energy content even when abundant in the environment.
Deep-sea Research Part I-oceanographic Research Papers, 2011
Long-finned pilot whales (Globicephala melas), Risso's dolphins (Grampus griseus), melon-headed w... more Long-finned pilot whales (Globicephala melas), Risso's dolphins (Grampus griseus), melon-headed whales (Peponocephala electra), Cuvier's beaked whales (Ziphius cavirostris), Sowerby's beaked whales (Mesoplodon bidens), northern bottlenose whales (Hyperoodon ampullatus), sperm whales (Physeter macrocephalus), dwarf sperm whales (Kogia sima) and pygmy sperm whales (Kogia breviceps) make up the large community of deep-diving odontocetes occurring off the Bay of Biscay, northeast Atlantic. The ecology of these toothed cetaceans is poorly documented worldwide. The present study described their prey preferences from stomach content analysis and showed resource partitioning within the assemblage. The majority of the species appeared to be mostly teutophageous. Fish was an important food source only for the Sowerby's beaked whale and, to a lesser extent, for the long-finned pilot whale. In terms of foraging habitats inferred from prey composition, either pelagic oceanic or demersal neritic habitats were exploited by toothed whales in the Bay of Biscay, with only the long-finned pilot whale foraging in the two habitats. Finally, with more than 14,000 identified cephalopods from 39 species, the present study highlighted also the poorly known deep-sea cephalopod community off the Bay of Biscay using top predators as biological samplers.► New insights in the foraging ecology of poorly documented deep-diving odontocetes. ► Successful example of food segregation within a top predator community. ► First study using biological samplers on deep-sea cephalopod fauna living in the northern Atlantic.
We investigated the status of the grey seal in the Molène archipelago, western Brittany, where a ... more We investigated the status of the grey seal in the Molène archipelago, western Brittany, where a Marine National Park is planned. We combined regular censuses, photo-identification and satellite telemetry to investigate trends in grey seal abundance, site fidelity, individual movements and haulout site use. Individual movements and seasonal variations in abundance suggest that the seals used the Molène archipelago alternatively with other haulout sites of the South-west British Isles during their annual cycle. Nine out of 16 seals fitted with Satellite Relay Data Loggers (SRDLs) moved to the Isles of Scilly, English Cornwall, Wales or the Channel islands. On average the seals spent 85% of their time Near Haulout, 56.8% of which in the Molène archipelago. Overall the seals spent 66% of their tracking time within the boundaries of the Marine National Park. From 1997 to 2000 in the Molène archipelago, we observed a peak in number during the moulting season (mean = 49.8 seals) and a lower abundance during the breeding season (mean = 38.3 seals). The sex ratio was strongly skewed towards males during the moult (between 3.1 and 5.3–1), and was close to 1:1 during the summer. Inter-annual site fidelity outside the breeding season was very high, varying from 70% to 95% of identified seals, suggesting that the observed movements constitute rotations rather than random dispersion. From 1991/1994 to 1997/2000, the mean number of seals counted at haulout sites increased by 7%, close to the rates of increase observed in the core population of the British Isles at the same period. The Marine National Park may be too restricted for the overall conservation of the population but management plans should be aimed at preserving the characteristics of the habitat for the grey seal.
As part of a larger project on the feeding ecology of large pelagic predators off the Bay of Bisc... more As part of a larger project on the feeding ecology of large pelagic predators off the Bay of Biscay, this study analyses the diet of the swordfish, Xiphias gladius. Stomachs were collected from 86 swordfish. The diet was analysed in terms of prey occurrence, relative abundance, reconstituted mass, and size distribution. It consisted mainly of fish, 40.5% by mass (%M) and cephalopods, 59.3%M; crustaceans, 0.2%M, were considered secondary prey. When considering only the fresh fraction to allow for differential digestion rates, these figures were 77.3%M, 22.7%M, and trace amounts, respectively. Lanternfish, including Notoscopelus kroeyeri and Symbolophorus veranyi, were abundant, but paralepidids, Atlantic pomfret (Brama brama), and the squid Todarodes sagittatus, Ommastrephes bartramii, and Gonatus steenstrupi, dominated the diet by mass. The overall prey size range was 11e1420 mm, but sizes of 60e360 mm accounted for 80% of the distribution by number and of 140e760 mm for 80% of the distribution by mass. Intraspecifically, larger swordfish ate larger prey as a result of a change in species composition of the diet. The swordfish appears to show feeding plasticity both between different areas and between animals in the same area.
Spitz, J., Mourocq, E., Schoen, V., and Ridoux, V. 2010. Proximate composition and energy content... more Spitz, J., Mourocq, E., Schoen, V., and Ridoux, V. 2010. Proximate composition and energy content of forage species from the Bay of Biscay: high-or low-quality food? -ICES Journal of Marine Science, 67: 909 -915.
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