Season variation in nutrient composition of Alaskan walleye pollock

2004 ◽  
Vol 82 (9) ◽  
pp. 1408-1415 ◽  
Author(s):  
David D Kitts ◽  
Minh Dieu Huynh ◽  
Chun Hu ◽  
Andrew W Trites
Keyword(s):  
Lipid Content ◽  
Gonad Development ◽  
Nutrient Content ◽  
Protein Digestibility ◽  
Analysis Data ◽  
Dry Mass ◽  
Walleye Pollock ◽  
Steller Sea Lions ◽  
Crude Lipid ◽  
Sea Lions

A popular hypothesis for the noted steady decline in the population of Steller sea lions, Eumetopias jubatus (Schreber, 1776), in the regions from Prince William Sound through the Aleutian Islands relates to their nutritional status. Sea lion diets appear to have shifted from primarily small schooling fatty fishes to low-fat fish such as walleye pollock, Theragra chalcogramma (Pallas, 1814). We examined the seasonal changes in proximate nutrients of pollock collected in the Bering Sea. Mean energy density (dry mass) of pollock peaked in October then declined and remained low throughout winter. Energy recovery occurred in the summer months with strong recovery observed in female fish caught in July. Contrary to whole fish carcass energy contents, both total protein and moisture contents were at their highest levels in winter (January) when total crude lipid content was at its lowest (p < 0.05). This trend gradually declined to its lowest levels in the fall when lipid content was high. The decline in total lipids during winter seasons appeared to parallel gonad development during the prespawning period. Sex differences in energy densities were not found. Proximate analysis data for moisture, protein, ash, and lipid content also did not show any significant variation between males and females. Protein digestibility of pollock was higher (p < 0.05) in the summer than in the spring, but not different for winter or fall. We concluded that the nutrient content of walleye pollock may have some impact on the Steller sea lions that feed on them, particularly the energetic value that appears to be low during important feeding periods for this marine mammal.

Comparing total body lipid content of young-of-the-year Steller sea lions among regions of contrasting population trends

2016 ◽  
Vol 32 (4) ◽  
pp. 1200-1218 ◽  
Author(s):  
Lorrie D. Rea ◽  
Brian S. Fadely ◽  
Sean D. Farley ◽  
Julie P. Avery ◽  
Wendy S. Dunlap-Harding ◽  
...  
Keyword(s):  
Lipid Content ◽  
Population Trends ◽  
Body Lipid ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Young Of The Year ◽  
Total Body

scholarly journals A Survey of the Nutrient Composition of Some Commercial Fish Feeds Available in Bangladesh

2005 ◽  
Vol 18 (1) ◽  
Author(s):  
M.A. KADER ◽  
M.A. HOSSAIN ◽  
M.R. HASAN
Keyword(s):  
Protein Content ◽  
Lipid Content ◽  
Nutrient Content ◽  
Fish Feed ◽  
Mineral Contents ◽  
Crude Lipid ◽  
Commercial Fish ◽  
Nutrient Contents ◽  
Fish Feeds ◽  
Lower Protein

A study was undertaken to analyse and compare the nutrient content of some commercial fish feeds available in Bangladesh through chemical analysis. The commercial fish feeds collected from the markets were Quality Feeds Ltd. (QF), Aftab Feed Products Ltd. (AF), Saudi-Bangla Fish Feed Ltd. (SBF), Paragon Feeds Ltd. (PF) and AIT Feeds Ltd. (AIT). Proximate composition such as moisture, crude protein, crude lipid, ash, fibre and NFE (nitrogen free extract), and some of the macro minerals such as Ca, P, Na, K and S were analysed. In general, there was no large variation between analysed and company declared nutrient contents of different feeds except the protein and lipid content of some feeds. However, two pangas feeds such as Surovi (nursery and grower) of QF had much lower protein content (27.57% and 20.24%) compared to 32% and 25% protein value respectively declared by the company. Similarly, large (more than 5%) differences between the analysed and company declared protein content was observed in case of carp starter and grower feeds of QF. On the other hand, analysed protein content of all feeds of SBF was more than that declared by the company except for special shrimp feed which had slightly lower (1%) protein compared to the company declared value. Pangas feeds (grower I and II) of PF had about 3% lower protein than the company declared value. The analysed lipid contents of all feeds were higher than the company declared values except nursery feeds of QF which had about 1-2% less lipid content compared to the company declared value. Fibre contents of different feeds analysed were much higher (3-5%) than the company declared values. The analysed mineral contents in all the feeds were higher than the recommended mineral requirement for fishes. The results of the study showed that on the basis of nutrient content feeds from Saudi-Bangla Fish Feed Ltd. is better than other feeds.

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 The diet of free-ranging male Steller sea lions (Eumetopias jubatus) in the eastern Bering Sea: a retrospective analysis based on stomach contents of an endangered pinniped

2019 ◽  
Vol 97 (3) ◽  
pp. 195-202
Author(s):  
E.H. Sinclair ◽  
W.A. Walker ◽  
P.J. Gearin
Keyword(s):  
Bering Sea ◽  
Stomach Contents ◽  
Walleye Pollock ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Eastern Bering Sea ◽  
Ice Edge ◽  
Myoxocephalus Scorpius ◽  
Free Ranging

This study illuminates historical diet and foraging locations of endangered western U.S. stock Steller sea lions (Eumetopias jubatus (Schreber, 1776)). Prey were identified from stomachs of 22 males collected in the eastern Bering Sea from the ice edge in March 1985 and nearshore St. Paul Island in September–October 1985 and 1986. Percent frequency of occurrence (PFO) and percent number (PN) were highest for walleye pollock (Gadus chalcogrammus Pallas, 1814; PFO 69%, PN 15%, mean length 17 cm), Pacific herring (Clupea pallasii Valenciennes in Cuvier and Valenciennes, 1847; PFO 62%, PN 16%, mean length 26 cm), shorthorn sculpin (Myoxocephalus scorpius (Linnaeus, 1758); PFO 54%, PN 30%), and Pacific giant octopus (Enteroctopus dofleini (Wülker, 1910); PFO 39%, PN 8%, mean weight 31 kg) in spring, and northern rock sole (Lepidopsetta polyxystra Orr and Matarese, 2000; PFO 78%, PN 47%, mean length 35 cm), Pacific cod (Gadus macrocephalus Tilesius, 1810; PFO 56%, PN 12%, mean length 62 cm), walleye pollock (PFO 44%, PN 7%, mean length 49 cm), and red Irish lord (Hemilepidotus hemilepidotus (Tilesius, 1811); PFO 11%, PN 9%) in fall. Species of Cryptacanthidae, Liparidae, and Zoarcidae were highly represented and exclusive to spring collections. Predictable seasonal concentrations and movements of mature prey along frontal boundaries of the continental shelf and ice edge may be critical to male Steller sea lion fitness during the non-breeding season.

Diet composition of Steller sea lions (Eumetopias jubatus) in Frederick Sound, southeast Alaska: a comparison of quantification methods using scats to describe temporal and spatial variabilities

2015 ◽  
Vol 93 (5) ◽  
pp. 361-376 ◽  
Author(s):  
D.J. Tollit ◽  
M.A. Wong ◽  
A.W. Trites
Keyword(s):  
Pacific Salmon ◽  
Biomass Energy ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Southeast Alaska ◽  
Merluccius Productus ◽  
Sea Lions ◽  
Sampling Protocols ◽  
Dietary Indices

We compared eight dietary indices used to describe the diet of Steller sea lions (Eumetopias jubatus (Schreber, 1776)) from 2001 to 2004 in Frederick Sound, southeast Alaska. Remains (n = 9666 items) from 59+ species categories were identified from 1684 fecal samples (scats) from 14 collection periods. The most frequently occurring prey were walleye pollock (Theragra chalcogramma (Pallas, 1814) = Gadus chalcogrammus Pallas, 1814; 95%), Pacific herring (Clupea pallasii Valenciennes in Cuvier and Valenciennes, 1847; 30%), Pacific hake (Merluccius productus (Ayres, 1855); 29%), and arrowtooth flounder (Atheresthes stomias (Jordan and Gilbert, 1880) = Reinhardtius stomias (Jordan and Gilbert, 1880); 21%). These species, along with Pacific salmon (genus Oncorhynchus Suckley, 1861) and skate (genus Raja L., 1758), accounted for 80%–90% of the reconstructed biomass and energy contribution, with pollock contributing 37%–60%. Overall, 80% of fish were 14–42 cm long and mainly pelagic, though 40% of scats contained benthic-associated prey. Steller sea lions switched from adult pollock to strong cohorts of juvenile pollock, and took advantage of spawning concentrations of salmon in autumn and herring in late spring and summer, as well as a climate-driven increase in hake availability. Observed temporal and site differences in diet confirm the need for robust long-term scat sampling protocols. All major indices similarly tracked key temporal changes, despite differences in occurrence and biomass-energy-based diet estimates linked to prey size and energy-density effects and the application of correction factors.

Maternal attendance patterns of Steller sea lions (Eumetopias jubatus) from stable and declining populations in Alaska

2003 ◽  
Vol 81 (2) ◽  
pp. 340-348 ◽  
Author(s):  
Linda L Milette ◽  
Andrew W Trites
Keyword(s):  
Prey Availability ◽  
A Priori ◽  
Population Decline ◽  
Perinatal Period ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
First Feeding ◽  
Attendance Patterns ◽  
The Mean

Maternal attendance patterns of Alaskan Steller sea lions (Eumetopias jubatus) were compared during the summer breeding seasons in 1994 and 1995 at Sugarloaf Island (a declining population) and Lowrie Island (a stable population). Our goal was to determine whether there were differences in maternal attendance between the two populations that were consistent with the hypothesis that lactating Steller sea lions in the area of decline were food-limited during summer. Our a priori expectations were based on well-documented behavioural responses of otariids to reduced prey availability. We found that foraging trips were significantly shorter in the area of population decline, counter to initial predictions. The mean length of foraging trips in the declining area was 19.5 h compared with 24.9 h in the stable area. In contrast, the mean perinatal period (time between parturition and first feeding trip) was significantly longer in the area of decline (9.9 versus 7.9 days), again countering initial predictions. The mean length of shore visits for the declining population was also significantly longer (27.0 h compared with 22.6 h where the population was stable). For both populations, the mean time that mothers foraged increased as pups grew older, whereas the time that they spent on shore with their pups became shorter. Behavioural observations of maternal attendance patterns are inconsistent with the hypothesis that lactating Steller sea lions from the declining population had difficulty obtaining prey during summer.

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