The development of migratory strategies that enable juveniles to survive to sexual maturity is critical for species that exploit seasonal niches. For animals that forage via breath-hold diving, this requires a combination of both... more
The development of migratory strategies that enable juveniles to survive to sexual maturity is critical for species that exploit seasonal niches. For animals that forage via breath-hold diving, this requires a combination of both physiological and foraging skill development. Here, we assess how migratory and dive behaviour develop over the first year of life for a migratory Arctic top predator, the harp seal Pagophilus groenlandicus, tracked using animal-borne satellite relay data loggers. We reveal similarities in migratory movements and differences in diving behaviour between 38 juveniles tracked from the Greenland Sea and Northwest Atlantic breeding populations. In both regions, periods of resident and transitory behaviour during migration were associated with proxies for food availability: sea ice concentration and bathymetric depth. However, while ontogenetic development of dive behaviour was similar for both populations of juveniles over the first 25 days, after this time Greenland Sea animals performed shorter and shallower dives and were more closely associated with sea ice than Northwest Atlantic animals. Together, these results highlight the role of both intrinsic and extrinsic factors in shaping early life behaviour. Variation in the environmental conditions experienced during early life may shape how different populations respond to the rapid changes occurring in the Arctic ocean ecosystem.
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As sentinels of ecosystem health, high trophic level predators integrate information through all levels of the food web. Their tissues can be used to investigate spatiotemporal variability in foraging behaviour, and with the appropriate... more
As sentinels of ecosystem health, high trophic level predators integrate information through all levels of the food web. Their tissues can be used to investigate spatiotemporal variability in foraging behaviour, and with the appropriate analytical methods and tools, archived samples can be used to reconstruct past trophic interactions. Harp seal Pagophilus groenlandicus teeth collected in the 1990s from the Northwest Atlantic were analysed for bulk stable carbon and nitrogen isotopes (δ13Cbulk and δ15Nbulk), and compound-specific stable nitrogen isotopes of amino acids (δ15NAA) for the first time. We developed a fine-scale, annual growth layer group (GLG) dentine sub-sampling method corresponding to the second and third year of life. In accordance with previous diet studies, while there was individual variability in δ15Nbulk, δ13Cbulk and δ15NAA measurements, we did not detect significant differences in isotopic niche widths between males and females, or between GLGs. Relative troph...
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A sphincter on the inferior vena cava can protect the heart of a diving mammal from overload when elevated abdominal pressures increase venous return, yet sphincters are reported incompetent or absent in some cetacean species. We... more
A sphincter on the inferior vena cava can protect the heart of a diving mammal from overload when elevated abdominal pressures increase venous return, yet sphincters are reported incompetent or absent in some cetacean species. We previously hypothesized that abdominal pressures are elevated and pulsatile in fluking cetaceans, and that collagen is deposited on the diaphragm according to pressure levels to resist deformation. Here we tested the hypothesis that cetaceans generating high abdominal pressures need a more robust sphincter than those generating low pressures. We examined diaphragm morphology in seven cetacean and five pinniped species. All odontocetes had morphologically similar sphincters despite large differences in collagen content, and mysticetes had muscle that could modulate caval flow. These findings do not support the hypothesis that sphincter structure correlates with abdominal pressures. To understand why a sphincter is needed, we simulated the impact of oscillati...
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Research Interests: Zoology, Geography, Productivity, Ecology, Keystone species, and 3 moreFishery, Forage, and Forage Fish
Internal pressures change throughout a cetacean's body during swimming or diving, and uneven pressures between the thoracic and abdominal compartments can affect the cardiovascular system. Pressure differentials could arise from... more
Internal pressures change throughout a cetacean's body during swimming or diving, and uneven pressures between the thoracic and abdominal compartments can affect the cardiovascular system. Pressure differentials could arise from ventral compression on each fluke downstroke or by a faster equilibration of the abdominal compartment with changing ambient ocean pressures compared with the thoracic compartment. If significant pressure differentials do develop, we would expect the morphology of the diaphragm to adapt to its in vivo loading. Here, we tested the hypothesis that significant pressure differentials develop between the thoracic and abdominal cavities in diving cetaceans by examining diaphragms from several cetacean and pinniped species. We found that: (1) regions of cetacean diaphragms possess subserosal collagen fibres that would stabilize the diaphragm against craniocaudal stretch; (2) subserosal collagen covers 5-60% of the thoracic diaphragm surface, and area correlates...
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Although the stock relationships among harbour porpoise (Phocoena phocoena) in the Northwest Atlantic are unknown, it has been postulated that there are 4 local populations: Bay of Fundy/Gulf of Maine, Gulf of St. Lawrence, Newfoundland,... more
Although the stock relationships among harbour porpoise (Phocoena phocoena) in the Northwest Atlantic are unknown, it has been postulated that there are 4 local populations: Bay of Fundy/Gulf of Maine, Gulf of St. Lawrence, Newfoundland, and west Greenland. Data on the Newfoundland population are extremely limited. To determine growth rates and examine if these animals can be differentiated from other sub-populations on the basis of growth characteristics, 94 porpoises caught incidentally in fishing gear along the southeast coast of Newfoundland during the summers of 1990 and 1991 were examined. Most porpoises (56%) were ≤ 4 years of age. Maximum age was 9 for females and 12 for males. Growth rates were similar for both sexes until one year of age, after which females grew longer and weighed more than males of similar ages. Using the Gompertz growth model, asymptotic values for body length were 156.3 cm for females and 142.9 cm for males. Asymptotic weights were 61.6 kg and 49.1 kg ...
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Harp seals are capital breeders who give birth to single pups and nurse them with fat-rich milk for 12 days on pack ice in the North Atlantic under harsh environmental conditions. Our objective was to examine female attendance and nursing... more
Harp seals are capital breeders who give birth to single pups and nurse them with fat-rich milk for 12 days on pack ice in the North Atlantic under harsh environmental conditions. Our objective was to examine female attendance and nursing patterns under varying environmental conditions to determine whether these patterns change in response to changing weather conditions. The behaviour of 158 harp seal females and pups off north-eastern Newfoundland was recorded every 3 min during daylight hours. Air and water temperature, and wind speed were recorded at the beginning of each observation session. We constructed GAMM models to examine the importance of these variables in predicting attendance and nursing patterns. The best model for predicting attendance included time of day, air temperature, wind speed, and the interaction between wind and air temperature. The best model for predicting nursing included wind speed, air temperature and time of day. Females were more likely to attend their pups during the afternoon when solar radiation appeared to be high, but reduced attendance during high winds and/or low temperatures. The likelihood of attending females nursing during these poor weather conditions was greater than when conditions were better. Thus, females were less likely to be present when weather conditions were poor but when present, they were more likely to be provisioning their pups. This strategy may help these females defray the thermoregulatory demands on their limited resources while ensuring that their young attain weights that are likely to increase post-weaning survival and hence maternal fitness.
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The status of harbour porpoise (Phocoena phocoena) populations in the North Atlantic has raised numerous concerns. Although a number of factors that may be adversely affecting harbour porpoise populations have been identified, focus has... more
The status of harbour porpoise (Phocoena phocoena) populations in the North Atlantic has raised numerous concerns. Although a number of factors that may be adversely affecting harbour porpoise populations have been identified, focus has been on the impact of removals, primarily due to incidental catches in fishing gear. As a result, considerable efforts have been made to determine the levels and/or impact of bycatch in a number of areas. Unfortunately, many areas remain little studied. Currently, harbour porpoise are listed as threatened or vulnerable in many parts of their range. In order to determine if the current levels of removals are sustainable, information on stock identity and seasonal movements, population parameters, abundance, and the magnitude of removals is required. Although substantial progress has been made to improve our knowledge of these parameters in the last decade, significant gaps still exist. After reviewing the available data for each sub-population in the ...
Research Interests: Geography, Biology, Population, Fishing, Bycatch, and 3 moreHArbour, Fishery, and Threatened Species
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ABSTRACT There are virtually no data available on polycyclic aromatic hydrocarbons (PAH) in marine mammals. Total PAH concentrations were determined in terms of chrysene and petroleum hydrocarbon equivalents in muscle tissues of four... more
ABSTRACT There are virtually no data available on polycyclic aromatic hydrocarbons (PAH) in marine mammals. Total PAH concentrations were determined in terms of chrysene and petroleum hydrocarbon equivalents in muscle tissues of four species of seals and six species of whales from waters around Newfoundland and Labrador. Values expressed on a dry weight basis ranged from 0.10 to 1.21 ppm in terms of chrysene equivalents and 0.26 to 5.51 ppm in terms of petroleum equivalents. The relatively high levels found in some animals from fishing areas demonstrates a need for more comprehensive information on PAH in marine mammals.
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Page 1. HERPETOLOGICAL NOTES were similar to those of the first-year, late au-tumn frogs maintained in the laboratory for a long period of time. Furthermore, the admin-istration of testosterone to first-year frogs in autumn ...
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... was estimated to be 5.6 million (95% CI 3.9-7.2 m) in 2008 (Hammill and Stenson ... and southern Labrador, Canada indicated that diets vary spatially and temporally (Stenson unpublished data). ... for review at the second workshop,... more
... was estimated to be 5.6 million (95% CI 3.9-7.2 m) in 2008 (Hammill and Stenson ... and southern Labrador, Canada indicated that diets vary spatially and temporally (Stenson unpublished data). ... for review at the second workshop, and 3) longer term research needs (Bowen et al ...
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Harp seals breed in pack-ice, a substrate which can vary substantially between whelping patches depending on differing environmental and oceanographic conditions. This study demonstrates clear site differences in pup vocalizations and... more
Harp seals breed in pack-ice, a substrate which can vary substantially between whelping patches depending on differing environmental and oceanographic conditions. This study demonstrates clear site differences in pup vocalizations and mother pup behaviour between Northeast (Greenland Sea) and Northwest (Canadian Front) Atlantic harp seal populations. Classification trees showed a distinctive split between Front and Greenland Sea pup vocalisations. No clear sex differentiation in vocalizations was present for pups at the Front; 42% (n = 12) of male and 38% (n = 13) of female calls could be attributed to a given individual. In the Greenland Sea, 55% (n = 42) of female vocalisations were attributed to individuals compared with only 8% for males (n = 47). In addition behavioural observations of mother pup pairs were conducted (Front, n = 58; Greenland Sea, n = 78). Greenland Sea pups were found to nurse more, and were more alert than Front pups. Female attendance patterns also differed ...
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Research Interests: Zoology, Biology, Ecology, Population, Overfishing, and 13 moreFishing, Predation, Atlantic cod, Gadus morhua, Fishery, Biometrie, Stock, Ponte, Gadidae, Phoque, Phoca, Modelisation, and RECRUTEMENT
From 14 March to 6 April 2002 aerial surveys were carried out in the Greenland Sea pack ice (referred to as the “West Ice”), to assess the pup production of the Greenland Sea population of harp seals, Pagophilus groenlandicus. One... more
From 14 March to 6 April 2002 aerial surveys were carried out in the Greenland Sea pack ice (referred to as the “West Ice”), to assess the pup production of the Greenland Sea population of harp seals, Pagophilus groenlandicus. One fixed-wing twin-engined aircraft was used for reconnaissance flights and photographic strip transect surveys of the whelping patches once they had been located and identified. A helicopter assisted in the reconnaissance flights, and was used subsequently to fly visual strip transect surveys over the whelping patches. The helicopter was also used to collect data for estimating the distribution of births over time. Three harp seal breeding patches (A, B, and C) were located and surveyed either visually or photographically. Results from the staging flights suggest that the majority of harp seal females in the Greenland Sea whelped between 16 and 21 March. The calculated temporal distribution of births were used to correct the estimates obtained for Patch B. N...
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... used were similar to those developed and used previously for determining population size for harp and hooded seals in the northwest Atlantic (Hammill et al ... for pups that had left the ice or were not yet born at the time of the... more
... used were similar to those developed and used previously for determining population size for harp and hooded seals in the northwest Atlantic (Hammill et al ... for pups that had left the ice or were not yet born at the time of the survey (Myers and Bowen, 1989; Stenson et al ...
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In this paper, we estimate the pup production of harp seals ( Pagophilus groenlandicus ) using generalized additive models (GAMs) based on thin-plate regression splines. The spatial distribution of seal pups in a patch is modelled using... more
In this paper, we estimate the pup production of harp seals ( Pagophilus groenlandicus ) using generalized additive models (GAMs) based on thin-plate regression splines. The spatial distribution of seal pups in a patch is modelled using GAMs, and the pup production is estimated by numerically integrating the model over a fine grid area of the patch. Closed form expression for estimation of the the standard error of the pup production estimate is derived. The estimators are applied to simulated seal populations to investigate their properties. The results show that the proposed pup production estimator is comparable with the conventional pup production estimator. However, the bias of the standard error estimator of the proposed method is much lower than the bias of the conventional standard error estimator. The decrease of standard error bias results in a considerable reduction of the coefficient of variation estimate using the proposed GAM-based method. The proposed method is also a...
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Andersen, J. M., Wiersma, Y. F., Stenson, G. B., Hammill, M. O., Rosing-Asvid, A., and Skern-Maurizen, M. 2013. Habitat selection by hooded seals (Cystophora cristata) in the Northwest Atlantic Ocean. – ICES Journal of Marine Science,... more
Andersen, J. M., Wiersma, Y. F., Stenson, G. B., Hammill, M. O., Rosing-Asvid, A., and Skern-Maurizen, M. 2013. Habitat selection by hooded seals (Cystophora cristata) in the Northwest Atlantic Ocean. – ICES Journal of Marine Science, 70:173–185. We examined annual habitat use for 65 hooded seals (32 adult females, 17 adult males, and 16 juveniles) equipped with satellite relay data loggers (SRDLs) in spring or summer during five field seasons (2004–2008). A combined approach using first passage time (FPT) analysis and a generalized additive model (GAM) was applied to test for habitat selection, with a focus on environmental parameters of depth, slope, ice, sea surface temperature (SST), and chlorophyll. The models were run on adult males, adult females, and juveniles separately, and the results identified SST, depth, and chlorophyll as the most important factors influencing habitat selection across all categories. Furthermore, males and females preferred similar habitat conditions,...
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Frie, A. K., Fagerheim, K-A., Hammill, M. O., Kapel, F. O., Lockyer, C., Stenson, G. B., Rosing-Asvid, A., and Svetochev, V. 2011. Error patterns in age estimation of harp seals (Pagophilus groenlandicus): results from a transatlantic,... more
Frie, A. K., Fagerheim, K-A., Hammill, M. O., Kapel, F. O., Lockyer, C., Stenson, G. B., Rosing-Asvid, A., and Svetochev, V. 2011. Error patterns in age estimation of harp seals (Pagophilus groenlandicus): results from a transatlantic, image-based, blind-reading experiment using known-age teeth. – ICES Journal of Marine Science, 68: 1942–1953. Blind readings of known-age samples are the ultimate quality control method for age estimates based on hard tissues. Unfortunately, this is often not feasible for many species because of the scarcity of known-age samples. Based on a unique collection of known-age teeth of harp seals (age range: 1–18 years), ageing errors were evaluated in relation to true age, reader experience, sex, and tooth format (images vs. originals). Bias was estimated by linear models fitted to deviations from true age, and precision was estimated as their residual standard error. Image-based blind readings of 98 tooth sections by 14 readers, representing different lev...
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Abstract. Remains of large marine animals that wash onshore can be difficult to identify due to decomposition and loss of external body parts, and in consequence may be dubbed “sea monsters.” DNA that survives in such carcasses can... more
Abstract. Remains of large marine animals that wash onshore can be difficult to identify due to decomposition and loss of external body parts, and in consequence may be dubbed “sea monsters.” DNA that survives in such carcasses can provide a basis of identification. One ...
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Research Interests: SST and Bathymetry
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Despite reduced fishing effort in many North Atlantic fisheries following collapse of fish stocks, concerns remain about levels of direct mortality of harbour porpoise (Phocoena phocoena), primarily through incidental catches in fishing... more
Despite reduced fishing effort in many North Atlantic fisheries following collapse of fish stocks, concerns remain about levels of direct mortality of harbour porpoise (Phocoena phocoena), primarily through incidental catches in fishing gear. Although harbour porpoise incidental catch is known to occur in several fisheries along the coast of Newfoundland and Labrador, Canada, there are no reliable quantitative estimates for the last decade when the commercial fisheries have undergone major changes in effort and target species. Based on incidental catch rates derived using different reporting methods, with net-days as measures of effort and fishing trips as sampling units, the potential number of incidental catches of harbour porpoises in several gillnet fisheries in Newfoundland waters was estimated for the years 2001, 2002 and 2003. Confidence intervals were calculated using re-sampling techniques. Incidental catches of small cetaceans were estimated to be 862 in 2001, 1,428 in 200...
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In order to determine the potential impact of seals on commercial fish stocks in the Northwest Atlantic, it is necessary to have accurate estimates of the abundance of each species. Recent information on the abundance and catches of harp... more
In order to determine the potential impact of seals on commercial fish stocks in the Northwest Atlantic, it is necessary to have accurate estimates of the abundance of each species. Recent information on the abundance and catches of harp (Phoca groenlandica), hooded (Cystophora cristata), grey (Halichoerus grypus), harbour (Phoca vitulina), ringed (Phoca hispida) and bearded (Erignathus barbatus) seals is summarized.