Fatty acld signature analysis was used to investigate the diet and the spatial scales of foraging in harbor seals Phoca vituljna richardsi in Prince William Sound (PWS) and elsewhere in the Gulf of Alaska. Blubber samples collected in 1994 and 1995 from 104 harbor seals from PWS, Kodiak Island, and southeast Alaska were analyzed for fatty acid composition. A total of 163 potential prey samples representing 10 taxa were collected and individually analyzed for total fat content and fatty acid composition. Approximately 70 fatty acids and isomers were found in both harbor seals and their prey. Classification and regression tree analysis was used to classify seals and prey according to their fatty acid signatures. Large differences were found in the fatty acid composition of blubber from seals sampled at Kodiak, southeast Alaska and PWS, over a broad geographical scale of 400 to 800 km. Additionally, fatty acid signatures distinguished seals from different regions within PWS, as well as on finescale resolutions of specific haulout sites within 9 to 15 km of one another These findings suggest that seals forage site-specifically. These conclusions are supported by prey fatty acid patterns, which also differed on similarly small spatial scales within PM'S. Not only could prey species such as herring Clupea pallasi and pollock Theragra chalcogramma be differentiated from one another using fatty acid signatures, but they could also be distinguished by size-class and location within PWS, reflecting differences in diet with age and as well as with fine-scale habitat. Results from this study are consistent with both satellite data from tagged harbor seals and stomach content analyses of forage fish species In PWS. Although preliminary, analyses suggest that large herring and pollock, as well as flatfish, may have dominated the diet of seals in southern PWS, whereas diets of seals in northern and eastern PWS may have been compr~sed more of small size classes of herring and pollock, and perhaps other items such as cephalopods, sandlance Arnmodytes hexapterus, cod Gadus macrocephalus, and shrimp. We conclude that fatty acid signature analysis will be an important contribution to understanding marine food webs in estuarine and other marine environments.

We determined the fat content and fatty acid composition of 26 species of fish and invertebrates (n = 1153) that are primary forage species of piscivorous seabirds and marine mammals in Prince William Sound (PWS), Alaska. Flatfish, shrimps and octopus had the lowest average fat contents (~1.0%), although some cods, as well as juvenile walleye pollock Theragra chalcogramma, Pacific herring Clupea harengus pallasi and pink salmon Oncorhynchus gorbuscha also ranged as low as 0.5 to 0.7% fat. The highest fat contents were found in eulachon Thaleichthys pacificus (25%), adult herring (21%) and the squid Berrytheuthis magister (5 to 13%). Within species, fat content varied mostly with season, but also with size. Fatty acid signatures generally distinguished forage species, with up to 95% of individuals correctly classified using either discriminant or classification and regression tree (CART) analyses. Discriminant plots provided insight into the relationships between fatty acid signatures of different species. Species with similar life histories and diets clustered closer together, while those with the greatest differences in ecology differed most in their fatty acid patterns. Within some species, changes in fatty acid signatures were apparent with increasing size and were consistent with known dietary shifts reported from stomach contents analyses. Furthermore, fatty acid signatures of Age 0 (yr) pollock and herring in PWS were consistent with previous stomach contents analysis that indicated annual differences in the timing of dietary changes from eating zooplankton to piscivory. Overall, when size/age classes were taken into account, species classification using fatty acid signatures was improved. Our findings have important implications for evaluating diets and food web interactions of fish stocks, as well as at higher trophic levels. Despite individual variation within species, our results indicate that fatty acid signatures accurately characterize forage species in this ecosystem, and consequently can be used to study and perhaps estimate the species composition of diets of their predators. KEY WORDS: Fatty acids · Forage fish · Food webs · Trophic interactionsResale or republication not permitted without written consent of the publisher

Analysis of stomach contents of ringed seals (Phara hispidu) collected at eight locations along the Alaskan coast showed significant seasonal and regional difrerences in diet. During the spring-summer period saffron cod (Eleginus gmcilis) was the most important food item in the nearshore zone of the northeastern Bering and southeastern Chukchi Seas. In that period shrimps (Pundulus spp., Eualus spp., Lebbeus polaris, and Crungon septc~rnspinssu) were the major food in the northcentral Bering Sea, hyperiid amphipods (Pamthemisto libellula) in the central Beaufort Sea and euphausiids (Tlzysur~oessa spp.) in the boundary region (Barrow area) between the Chukchi and Beaufort seas. During late summer-early autumn hyperiid amphipocts were important foods in the central Beaufort and the southeastern Chukchi. The autumn diet of seals in Norton Sound included mainly sagron cod During winter-early spring Arctic cod (Boreogucius saida) predominated the diet at all localities. During spring and early summer in the northeastern Bering and southeastern Chukchi seas the amount of saffron cod consumed was directly correlated with age. In the Beuufort Sea during autumn and winter Arctic cod were eaten in similar amounts by all age-classes. An analysis of the energy value and quantities of prey consumed indicates that prey species that occur in concentrations (Arctic and saftion cods, hyperiid amphipods, euphausiids and some shrimps) are of particular importance in the annual nutrition of ringed seals. These seals may be food limited in areas and during times when these kinds of prey are not available. . 1980. Variability in the diet of ringed seals, Plzoeu kispidu, in Alaska. Can. J. Fish. Aquat. Sci. 37: 2254-2261. 11 existe des differences saisonnikres et regionales nlarquCes de regime alimentaire chez le phoque an11elC (Plzow lzispidu), comme le dCmontre I'analyse des contenus stomacaux d'Cchantillons recueillis h huit endroits le long de la c8te de 1'Alaska. Dans la pkriode printemps-6tC, la morue arctique (Elt>piilus gmcilis) est l'aliment le plus important d+ns la zone littorale du nordest de la mer de Bering et du sud-est de la rner de Tchouktche. A cette Cpoque, les crevettes (Paizdalus spy., Eualus spp., Lebbeus polaris et Cran,qon septemspinosa) constituent l'aliment principal dans le centre-nord de la rner de Bering, les amphipodes hypkriides (P~~mthc~rnisto libtdlula) dans le centre de la rner de Beaufort et les euphausides (Tl~ysurzoessa spp.) dans la region frontalikre (region de Barrow) entre les mers de Tchouktche et de Reaufort. En fin d'et6 et dCbut d'automne, les amphipodes hypkriides sont des aliments importants dans le centre de la rner de Beaufort et le sud-est de la mer de Tchouktche. Bans la baie Norton, le rCgime automnal des phoques est constituk en grande partis par de la morue arctique. En hiver et au debut du printemps, le saida (Boreogadus saida) prCdomine dans le regime h tous lec endroits. Au printemps et debut de l'kti, la quantite de rnorue arctique consomm& est fonction directe de ]'Age dans le ...

We used aerial counts to monitor the trend in numbers of harbor seals, Phoca vitulina richardsi, in Prince William Sound, Alaska, following the 1989 Exxon Valdez oil spill. Repetitive counts were made at 25 haul‐out sites during the annual molt period each year from 1990 through 1997. A generalized linear model indicated that time of day, date, and time relative to low tide significantly affected seal counts. When Poisson regression was used to adjust counts to a standardized set of survey conditions, results showed a highly significant decline of 4.6% per year. Unadjusted counts indicated a slight, but not statistically significant, decline in the number of seals. The number of harbor seals on the trend‐count route in eastern and central PWS has been declining since at least 1984, with an overall population reduction of 63% through 1997. Programs to monitor long‐term changes in animal population sizes should account for factors that can cause short‐term variations in indices of abundance. The inclusion of such factors as covariates in models can improve the accuracy of monitoring programs.

Harbor seal pups are highly precocial and can swim and dive at birth. Such behavioral maturity suggests that they may be born with mature body oxygen stores or that stores develop quickly during the nursing period. To test this hypothesis, we compared the blood and muscle oxygen stores of harbor seal pups, yearlings, and adults. We found that pups had smaller oxygen stores than adults (neonates 57%, weaned pups 75%, and yearlings 90% those of adults), largely because neonatal myoglobin concentrations were low (1.6+/-0.2 g% vs. 3.8+/-0.3 g% for adults) and changed little during the nursing period. In contrast, blood oxygen stores were relatively mature, with nursing pups having hematocrit (55%+/-0.2%), hemoglobin (21.7+/-0.4 g%), and blood volume (12.3+/-0.5 mL/kg) only slightly lower than the corresponding values for adults (57%+/-0.2%, 23.8+/-0.3 g %, and 15.0+/-0.5 mL/kg). Because neonatal pups had relatively high metabolic rates (11.0 mL O2/kg min), their calculated aerobic dive limit was less than 50% that of adults. These results suggest that harbor seals' early aquatic activity is primarily supported by rapid development of blood, with immature muscle oxygen stores and elevated use rates limiting aerobic diving ability.

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ABSTRACT-At least fi ve stocks of beluga whales, Delphinapterus leucas, are found in Alaska waters : Beaufort Sea, eastern Chukchi Sea, eastern Bering Sea, Bristol Bay, and Cook Inlet. The two northernmost stocks (Beaufort Sea and eastern Chukchi Sea)

ABSTRACT. Current and historical information about food habits of bearded seals, Erignurhus burbutus, are presented. Shrimps, crabs, and clams are overall the most important prey. Proportions of different prey in the diet vary with age of seals, location, and time of year. Foods of male and female seals are similar. Young seals eat proportionally more shrimps than do older animals. Recently, clams were important in the diet only in Norton Sond and near Wainwright, and only during late spring and summer. Greatest quantities of food were found in stomachs of seals which had eaten mostly clams. In Bering Strait, seals taken in spring 1958 and 1967 had consumed large quantities of clams, but this item was only a minor fraction of foods in 1975-79.