Diet of endangered Steller sea lions (Eumetopias jubatus) in the Aleutian Islands: new insights from DNA detections and bioenergetic reconstructions

2017 ◽  
Vol 95 (11) ◽  
pp. 853-868 ◽  
Author(s):  
Dominic Tollit ◽  
Lowell Fritz ◽  
Ruth Joy ◽  
Kristi Miller ◽  
Angela Schulze ◽  
...  
Keyword(s):  
Aleutian Islands ◽  
Eumetopias Jubatus ◽  
Pacific Cod ◽  
Hard Part ◽  
Sea Lions ◽  
Important Prey ◽  
Enteroctopus Dofleini ◽  
Gadus Macrocephalus ◽  
Atka Mackerel ◽  
Pleurogrammus Monopterygius

The endangered western stock of Steller sea lion (Eumetopias jubatus (Schreber, 1776)) still declines in the western Aleutian Islands and accurate diet information is vital to test leading hypotheses. We undertook the first bioenergetic diet reconstruction using both molecular and hard part prey identifications from >600 scats collected in March–April 2008 and 2012. Atka mackerel (Pleurogrammus monopterygius (Pallas, 1810)) remained a primary prey (17%–27% by energy), but large (mean 60 cm) Pacific cod (Gadus macrocephalus Tilesius, 1810) also emerged as important prey (20%–24%) in a more diverse diet than previously reported, with Cottidae and smooth lumpsucker (Aptocyclus ventricosus (Pallas, 1769)) also contributing ∼10%. DNA detections highlighted a potentially important and previously underestimated prey, giant Pacific octopus (Enteroctopus dofleini (Wülker, 1910) (diet contribution 2%–15%, dependent on prey size assumptions). Although 504 unique DNA identifications resulted in significant increases for cephalopods, Pacific cod, and smooth lumpsucker, hard part alone species rankings were similar to composite ones and bioenergetic species rankings similar to occurrence-based ones. Retention or regurgitation of large cephalopod beaks, the removal of large cod heads, and skeletal fragility of lumpsuckers may explain these differences. DNA identifications provide valuable comparative and complementary prey occurrence data for pinnipeds, but composite diet estimates are optimal.

Diet diversity of Steller sea lions (Eumetopias jubatus) and their population decline in Alaska: a potential relationship

1997 ◽  
Vol 54 (6) ◽  
pp. 1342-1348 ◽  
Author(s):  
Richard L Merrick ◽  
M Kathryn Chumbley ◽  
G Vernon Byrd
Keyword(s):  
Population Decline ◽  
Gulf Of Alaska ◽  
Walleye Pollock ◽  
Aleutian Islands ◽  
Strong Positive Correlation ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Diet Diversity ◽  
Sea Lions ◽  
Atka Mackerel

We examined the diet of Steller sea lions (Eumetopias jubatus) during June-August 1990-1993 from six areas in the Aleutian Islands and Gulf of Alaska and related these diets to sea lion population changes that occurred during the period. Seven general prey categories were identified, but either walleye pollock (Theragra chalcogramma) or Atka mackerel (Pleurogrammus monopterygius) dominated in every area. The diversity of prey consumed varied among sites. Only the eastern Aleutian Islands area had all seven categories in the diet, and there, walleye pollock and Atka mackerel each made up around 30% of the diet. The remainder was composed mostly of small schooling fish (e.g., Pacific herring (Clupea pallasi) and salmon (Oncorhynchus spp.)). The diet in the Gulf of Alaska included mostly walleye pollock whereas the central and western Aleutian diet was composed mostly of Atka mackerel. Populations in the six areas decreased up to 49% during 1990-1994. A strong positive correlation (r = 0.949, P = 0.004) was found between diet diversity and the amount of decline in an area: as diet diversity decreased, populations decreased. This suggests that sea lions need a variety of prey available, perhaps to buffer significant changes in abundance of any single prey.

scholarly journals STATE OF STOCKS AND MODERN FISHERY OF ATKA MACKEREL PLEUROGRAMMUS MONOPTERYGIUS (PALLAS, 1810) IN THE OLYUTORSKY-NAVARINSKY AREA OF THE BERING SEA

2020 ◽  
Vol 200 ◽  
pp. 38-57
Author(s):  
A. O. Zolotov ◽  
O. G. Zolotov ◽  
Yu. K. Kurbanov
Keyword(s):  
Bering Sea ◽  
Gulf Of Alaska ◽  
Aleutian Islands ◽  
Commander Islands ◽  
Spawning Grounds ◽  
Spawning Stock ◽  
Atka Mackerel ◽  
Pleurogrammus Monopterygius ◽  
Commercial Stock ◽  
The Bering Sea

Atka mackerel Pleurogrammus monopterygius is one of the mass species of fam. Hexagrammidae that inhabits the boreal and subarctic waters of the North Pacific and forms two large populations in its western and eastern parts. Reproductive range of the eastern, Aleutian population extends from the Gulf of Alaska, along Aleutian Islands to Commander Islands, with the main spawning grounds at the Aleutians and in the southeastern Bering Sea. From these areas, the fish at early stages of ontogenesis spread widely in system of the Bering Sea currents to the western-southwestern Bering Sea, where the atka mackerel aggregations are formed on the external shelf at prominent capes, as Cape Olyutorsky. Dynamics of the atka mackerel stock in the Olyutorsky-Navarinsky area in 1994–2019 is presented on the base of bottom trawl surveys, fishery statistics, and open NOAA data. After the period of low stock in the middle 1990s, the atka mackerel abundance increased sharply to the maximum in 2006–2008, when the spawning stock in this area was about 9.5 . 103 t and the commercial stock about 14.0 . 103 t. Since that time, trend to decreasing is observed, with the spawning stock 3.6 . 103 t and the commercial stock 5.6 . 103 t in 2013, and recent stabilization at the low level with slight decline continuing. A possible reason of the sharp increase in 2000s could be the intensive transport of the atka mackerel juveniles from the main spawning grounds at Aleutian Islands to the area at Cape Olyutorsky. The catches of atka mackerel in the Olyutorsky-Navarinsky area in 1994–2018 corresponded well with its stock dynamics.

Prey competition between sympatric Steller sea lions (Eumetopias jubatus) and northern fur seals (Callorhinus ursinus) on Lovushki Island, Russia

2012 ◽  
Vol 90 (1) ◽  
pp. 110-127 ◽  
Author(s):  
J.N. Waite ◽  
V.N. Burkanov ◽  
R.D. Andrews
Keyword(s):  
Interspecific Competition ◽  
Russian Far East ◽  
Far East ◽  
Callorhinus Ursinus ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Fur Seals ◽  
Northern Fur Seals ◽  
Atka Mackerel

Approximately 1 000 Steller sea lions ( Eumetopias jubatus (Schreber, 1776); SSL) and 14 000 northern fur seals ( Callorhinus ursinus (L., 1758); NFS) breed sympatrically on Lovushki Island in the Russian Far East, creating the potential for interspecific competition for prey. An additional 13 000 – 14 000 juvenile NFS are present during the breeding season. The diets of breeding SSL and both breeding and juvenile NFS were examined through analysis of scats and spews collected during the breeding seasons of 2003, 2005, and 2007–2008. There were significant overlaps in the prey species and size selection of SSL and juvenile NFS. There were significant differences between the diets of SSL and breeding NFS. SSL and juvenile NFS fed primarily on Atka mackerel ( Pleurogrammus monopterygius (Pallas, 1810)), while breeding NFS fed on cephalopods, salmon (genus Oncorhynchus Suckley, 1861), Atka mackerel, and northern smoothtongue ( Leuroglossus schmidti Rass, 1955). The partitioning of resources between breeding animals has allowed both species to coexist within the same region and likely reflected differences in foraging abilities and provisioning strategies of the adults and the fasting abilities of their pups. However, continued growth of the NFS population may lead to the exclusion of SSL owing to interspecific competition for prey.

A re-examination of the relationship between Steller sea lion (Eumetopias jubatus) diet and population trend using data from the Aleutian Islands

2019 ◽  
Vol 97 (12) ◽  
pp. 1137-1155 ◽  
Author(s):  
L. Fritz ◽  
B. Brost ◽  
E. Laman ◽  
K. Luxa ◽  
K. Sweeney ◽  
...  
Keyword(s):  
Energy Density ◽  
Population Trend ◽  
Population Trends ◽  
Aleutian Islands ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lion ◽  
Diet Diversity ◽  
Sea Lions ◽  
Using Data

Prey diversity and energy density have been linked to each other and to population trends in many studies of bird and mammal diets. We re-examined these relationships in Steller sea lions (Eumetopias jubatus (Schreber, 1776)) using data collected from the Aleutian Islands, where there has been a strong longitudinal gradient in population trend. Diet diversity and energy density metrics were similar in the western Aleutians, where sea lion counts declined consistently, and in the easternmost Aleutian area, where population trends improved significantly. We compared traditional deterministic diet diversity metrics with diversity scores based on an occupancy model that accounts for differences in sample size and uncertainty in prey group detection. This analysis indicated that there was no significant change in diet diversity over the 23-year study period or any significant differences across the Aleutian Islands. These results are consistent with prey abundance data from nine groundfish bottom trawl surveys conducted over the same period. While diet studies detail what Steller sea lions eat and provide an estimate of their energy intake, they provide only limited information on the energy expended to obtain their food or the consequences of their diet and foraging ecology on individual or population fitness.

Pollock and the decline of Steller sea lions: testing the junk-food hypothesis

2000 ◽  
Vol 78 (7) ◽  
pp. 1243-1250 ◽  
Author(s):  
David AS Rosen ◽  
Andrew W Trites
Keyword(s):  
Body Mass ◽  
Energy Content ◽  
Gulf Of Alaska ◽  
Aleutian Islands ◽  
Net Energy ◽  
Junk Food ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Gross Energy

The decline of Steller sea lions (Eumetopias jubatus) in the Gulf of Alaska and the Aleutian Islands may be the result of them eating too much pollock (a gadid fish) instead of a more balanced and diverse diet containing fattier fishes, such as herring or sandlance. We sought to test this junk-food hypothesis by feeding six captive Steller sea lions (ages 0.9-4.5 years) only pollock or herring. All sea lions gained mass while eating herring. However, eating only pollock for short periods (11-23 d) caused the study animals to lose an average of 6.5% of their initial body mass (0.6 kg/d) over an average feeding trial of 16 d (initial mass averaged 125 kg). The animals were allowed to eat as much pollock as they wanted but did not increase their food intake to compensate for the low energy they were receiving. The sea lions showed progressive metabolic depression while losing body mass on a pollock-only diet. The loss of body mass while eating pollock was due to the lower gross energy content of pollock versus herring, the higher cost of digesting pollock, and the increased energy loss from digesting the larger quantity of fish needed to compensate for the lower energy content of pollock. Thus, our sea lions would have had to eat 35-80% more pollock than herring to maintain similar net energy intakes. Results from our captive-feeding studies are consistent with the junk-food hypothesis and have serious implications for Steller sea lions that have been eating primarily pollock in the Gulf of Alaska and the Aleutian Islands.

scholarly journals Seasonal migratory patterns of Pacific cod (Gadus macrocephalus) in the Aleutian Islands

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
David R. Bryan ◽  
Susanne F. McDermott ◽  
Julie K. Nielsen ◽  
Dave Fraser ◽  
Kimberly M. Rand
Keyword(s):  
Movement Patterns ◽  
Partial Migration ◽  
Seasonal Migration ◽  
Aleutian Islands ◽  
Commercial Fishery ◽  
Pacific Cod ◽  
Cooperative Research ◽  
Important Species ◽  
Seasonal Movement ◽  
Gadus Macrocephalus

Abstract Background Pacific cod (Gadus macrocephalus) is an ecologically important species that supports a valuable commercial fishery throughout Alaska waters. Although its life history includes seasonal movement for spawning and feeding, little is known about its movement ecology. Here, we present results from the first study to use pop-up satellite archival tags (PSATs) to track the within-year movements of Pacific cod to understand their potential seasonal movement patterns within the Aleutian Islands. This study was part of a cooperative research project; tagging was conducted onboard commercial vessels during the winter fishing season while Pacific cod were aggregated to spawn in the central Aleutian Islands. Results Of the 36 PSATs deployed, we were able to obtain movement data from 13 Pacific cod that were at liberty between 60 and 360 days. We determined that three tagged Pacific cod were predated on by marine mammals and three were recaptured by the commercial fishery. Geolocation models were produced for four migrating individuals. Eight Pacific cod moved to a productive foraging ground near Seguam Island located 64 to 344 km from their release site and presumed spawning ground within a few weeks of their release. These movements indicate that some Pacific cod in the Aleutian Islands undergo seasonal migration. Three Pacific cod remained near their release locations (within 50 km) for more than 75 days suggesting the existence of partial migration in the population. Two Pacific cod undertook larger movements (378 and 394 km) during which they swam over deep passes and crossed several management boundaries highlighting the potential connectedness of Pacific cod throughout the Aleutian Islands. Conclusions This study provided important initial insights into the seasonal movement patterns of Pacific cod in the Aleutian Islands. Most tracked Pacific cod (77%) undertook migrations in the middle of March (64–394 km) from their winter spawning areas to summer foraging areas, but a few individuals remained in their capture location suggesting a partial migration strategy. Their ability to cross deep passes that were previously seen as potential barriers to movement has expanded our understanding of population connectivity.

scholarly journals IgE reactivity to Pacific cod (Gadus macrocephalus) fish allergens in dogs with canine atopic dermatitis

2019 ◽  
Vol 143 (2) ◽  
pp. AB67
Author(s):  
Ichiro Imanishi ◽  
Jumpei Uchiyama ◽  
Takako Matsuda ◽  
Keijiro Mizukami ◽  
Hidekatsu Shimakura ◽  
...  
Keyword(s):  
Atopic Dermatitis ◽  
Pacific Cod ◽  
Canine Atopic Dermatitis ◽  
Ige Reactivity ◽  
Pacific Cod Gadus Macrocephalus ◽  
Gadus Macrocephalus
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