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

Merrick, Richard L.; Chumbley, M. Kathryn; Byrd, G. Vernon

doi:10.1139/cjfas-54-6-1342

Cited by 77 publications

(112 citation statements)

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“…Pinnipeds are one group of vertebrates whose diet has been extensively studied due to population declines of some pinniped species (e.g. Merrick et al . 1997; Sinclair & Zeppelin 2002), declines in numbers of some of their prey (e.g.…”

Section: Introductionmentioning

confidence: 99%

Molecular scatology as a tool to study diet: analysis of prey DNA in scats from captive Steller sea lions

et al. 2005

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The DNA of prey present in animal scats may provide a valuable source of information for dietary studies. We conducted a captive feeding trial to test whether prey DNA could be reliably detected in scat samples from Steller sea lions (Eumetopias jubatus). Two sea lions were fed a diet of fish (five species) and squid (one species), and DNA was extracted from the soft component of collected scats. Most of the DNA obtained came from the predator, but prey DNA could be amplified using prey-specific primers. The four prey species fed in consistent daily proportions throughout the trial were detected in more than 90% of the scat DNA extractions. Squid and sockeye salmon, which were fed as a relatively small percentage of the daily diet, were detected as reliably as the more abundant diet items. Prey detection was erratic in scats collected when the daily diet was fed in two meals that differed in prey composition, suggesting that prey DNA is passed in meal specific pulses. Prey items that were removed from the diet following one day of feeding were only detected in scats collected within 48 h of ingestion. Proportions of fish DNA present in eight scat samples (evaluated through the screening of clone libraries) were roughly proportional to the mass of prey items consumed, raising the possibility that DNA quantification methods could provide semi-quantitative diet composition data. This study should be of broad interest to researchers studying diet since it highlights an approach that can accurately identify prey species and is not dependent on prey hard parts surviving digestion.

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Section: Introductionmentioning

confidence: 99%

Molecular scatology as a tool to study diet: analysis of prey DNA in scats from captive Steller sea lions

et al. 2005

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“…Thus, it is necessary to ex- (26), a time that coincides with the onset of otter declines. Although the exact cause of the pinniped decline is uncertain (27), it probably relates to reduced abundance and altered species composition of their prey (28). Recent population declines of piscivorous marine birds are consistent with this explanation (29).…”

Section: Discussionmentioning

confidence: 97%

“…These changes are attributed to the gradual collapse of the lungs and a decrease in lung volume that occur with increasing hydrostatic pressure during descent. Complete collapse of the alveoli occurs once dolphins have reached pressures equivalent to 65 to 70 m in depth (27,28). Likewise, the morphological structure of the respiratory system of elephant seals and Weddell seals indicates the capacity for collapse that may affect buoyancy during the course of a dive (29,30).…”

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confidence: 99%

Dolphins as Models for Cost Efficient Autonomous Underwater Vehicles

Williams¹

2000

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“…Previous studies had sampled their diets principally during daylight hours. In a comparative review of the literature, anadromous prey were not commonly noted in diets of various marine predators (Montevecchi et al , ; Juanes et al , ; Hall & Kress, ), but were an important prey item when sampling was conducted at relevant seasonal and spatial scales (Merrick et al , ; Orsi et al , ; Willette et al , ). As demonstrated here, when studies are conducted at appropriate spatial and temporal scales, alosine prey can be important in the diets of marine piscivores in the GOM.…”

Section: Discussionmentioning

confidence: 99%

Quantifying alosine prey in the diets of marine piscivores in the Gulf of Maine

McDermott

Bransome

Sutton

et al. 2015

Journal of Fish Biology

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The objectives of this work were to quantify the spatial and temporal distribution of the occurrence of anadromous fishes (alewife Alosa pseudoharengus, blueback herring Alosa aestivalis and American shad Alosa sapidissima) in the stomachs of demersal fishes in coastal waters of the north-west Atlantic Ocean. Results show that anadromous fishes were detectable and quantifiable in the diets of common marine piscivores for every season sampled. Even though anadromous fishes were not the most abundant prey, they accounted for c. 5-10% of the diet by mass for several marine piscivores. Statistical comparisons of these data with fish diet data from a broad-scale survey of the north-west Atlantic Ocean indicate that the frequency of this trophic interaction was significantly higher within spatially and temporally focused sampling areas of this study than in the broad-scale survey. Odds ratios of anadromous predation were as much as 460 times higher in the targeted sampling as compared with the broad-scale sampling. Analyses indicate that anadromous prey consumption was more concentrated in the near-coastal waters compared with consumption of a similar, but more widely distributed species, the Atlantic herring Clupea harengus. In the context of ecosystem-based fisheries management, the results suggest that even low-frequency feeding events may be locally important, and should be incorporated into ecosystem models.

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

Cited by 77 publications

References 0 publications

Molecular scatology as a tool to study diet: analysis of prey DNA in scats from captive Steller sea lions

Molecular scatology as a tool to study diet: analysis of prey DNA in scats from captive Steller sea lions

Dolphins as Models for Cost Efficient Autonomous Underwater Vehicles

Quantifying alosine prey in the diets of marine piscivores in the Gulf of Maine

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