Variability in the Diet of Ringed Seals, Phoca hispida, in Alaska

Abstract

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 ...

Distribution, abundance and biology of ringed seals (<i>Phoca hispida</i>): an overview

“…1966, Lowry et al 1980, Popov 1982, Weslawski et al 1994. The ringed seals in a given area typi-cally prey on no more than 10-15 prey species, and they tend to focus on only two to four of these (We slaw ski et al 1994).…”

“…Pelagic schooling fishes, mainly polar cod (Boreogadus saida) and secondarily saffron cod (Eleginus navaga) and other gadids, dominate the diet from late autumn through early spring (November-April) in some areas (Lowry et al 1980, Popov 1982. Young redfish (Sebastes spp.)…”

“…· are important prey items (Siegstad et al this volume). A wider variety of organisms is taken during late spring and summer, in some areas dominated by benthic crustaceans (mysids, shrimps and gammarid amphipods; Lowry et al 1980) and in others by polar cod (Bradstreet and Cross 1982). During late summer and early autumn, pelagic crustaceans become the main prey in offshore waters (hyperiid amphipods in Arctic regions and euphausiids in areas influenced by subarctic waters), and mysids in some nearshore areas (Lowry et al 1980, Siegstad et al this volume).…”

“…McLaren (1958aMcLaren ( , 1962 interpreted the observation that ringed seals are sometimes scarce in areas where food is abundant, but common in areas of low productivity, to mean that their distribution and abundance were driven less by food resources than by other factors, most notably sea-ice conditions. Lowry et al (1980), in contrast, emphasized the role of food availability and catchability in influencing the movements and productivity of ringed seals. Some authors have considered the density of ringed seals as a useful index of biological productivity.…”

“…Of the ice-associated phocids in the Arctic Basin, the ringed seal is the most widespread and is associated with the greatest variety of ice conditions. The diverse character of the ringed seal's diet ensures overlap with the diets of several other predators (Lowry et al 1980, Lowry and. Little overlap is evident, however, in the diets of ringed and bearded seals (Finley and Evans 1983), and these two ice-associated seals are ecologically separate in most respects (Burns 1981).…”