Star lore of the Hokkaido Ainu

Gotō, Akira

doi:10.4324/9780367809126-4

Cited by 1 publication

(9 citation statements)

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“…Eight feeding strategies were identified for spotted seals, and these strategies varied significantly among the three study regions. Feeding strategies focused on middle‐ and bottom‐layer species that inhabit coastal waters, which is consistent with previous reports on the feeding habits of spotted seals (Bukhtiyarov, 1990; Bukhtiyarov et al, 1984; Dehn et al, 2007; Fedoseev & Bukhtiyarov, 1972; Goto, 1999; Kato, 1982; Lowry et al, 1981; Nakaoka et al, 1986; Nikolaev & Skalkin, 1977; Pauly et al, 1998; Sobolevsky, 1996).…”

Section: Discussionsupporting

confidence: 87%

“…Studies conducted during the 1980s and 1990s on stomach content analysis using hunted individuals indicated that spotted seals were euryphagic and their diet varied considerably among the regions of Hokkaido (Goto, 1999; Kato, 1982; Nakaoka et al, 1986). In the northern Sea of Japan, spotted seals mainly fed on Alaska pollock ( Gadus chalcogramma ), a middle‐layer fish; and bottom‐layer fishes including cod ( Gadidae spp.…”

Section: Introductionmentioning

confidence: 99%

“…), and cephalopods ( Octopodidae spp.) in shallow nearshore waters (Goto, 1999). In the Sea of Okhotsk, spotted seals mainly fed on Alaska pollock, bottom‐layer fishes such as greenling ( Hexagrammidae spp.)…”

Section: Introductionmentioning

confidence: 99%

“…in deep offshore waters (Kato, 1982). Alaska pollock, which was common to both regions and was the main target of fisheries from the 1980s to the 1990s with annual catches of 300,000 to 800,000 tons throughout Hokkaido, was the most important prey species for spotted seals at that time (Goto, 1999; Kato, 1982; Mizushima & Torisawa, 2003). Along with the Pacific Ocean side of the Nemuro peninsula, however, spotted seals mainly fed on benthic octopus ( Octopus hongkongensis ) and bottom‐layer fishes such as cod, sand lance ( Ammoditidae ssp.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, the number of Steller sea lions migrating to northern Hokkaido has also increased (Hattori, 2020). Furthermore, annual commercial catches of Alaska pollock, cited by previous studies to be the most important prey species, have in recent years decreased to about 120,000 tons due to population decline (Goto, 1999; Hokkaido Agency, 2020; Miyake & Tanaka, 2006). With this decrease in Alaska pollock resources, the feeding habits of Steller sea lions have been reported to vary more greatly in each area.…”

Section: Introductionmentioning

confidence: 99%

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Estimation of feeding strategies of spotted seals (Phoca largha) migrating to three regions in Hokkaido, Japan

2023

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To understand the current feeding habits of spotted seals, this study estimates feeding strategies based on region, season, growth stage, and sex through the results of stomach content analyses, and compares its findings with feeding habits of the past.As a result of permutational multivariate analysis of variance (PERMANOVA), region, season, growth stage, and sex were detected as significant. Non-metric multidimensional scaling (nMDS), hierarchical cluster analysis, and the growth stages were categorized into age classes: Age 0 to age 4 years were classified as young, and age 5 and older were classified as adult. For the seasons, November and December were classified as winter, and February to May was classified as spring. And clustering with flexible mixture modeling, samples were divided into eight feeding strategies. In Rebun, the feeding strategy consisting of Octopodidae species showed a high total energy value and appeared at a high occurrence rate for both young and adult. In Saroma, Osmeridae species in winter and Clupeidae species in spring showed a high proportion. Both Osmeridae and Clupeidae species showed a high proportion in both seasons, all growth stages, and both sexes. In Rausu, adult was particularly dominant in Alaska pollock (Gadus chalcogramma) in spring, while young appeared at a high rate in Ammodytidae species. The present study has shown that seals have become particularly dependent on fish in all layers of the marine environment. In addition to drastic changes in their environment, the increase in the number of individuals of a competing species that is Steller sea lions in Rebun, and a decrease in fishery resources have made it impossible for spotted seals to take advantage of their high-energy feeding strategy mainly composed of Alaska pollock both Rebun and Rausu. As a result, regional differences in feeding strategies for both Rebun and Rausu have become more clearly differentiated than in the past, and the seals have flexibly changed their feeding strategies to accommodate the availability of prey species in their particular region. This study has succeeded in accurately classifying the feeding strategies of spotted seals in three disparate regions of Hokkaido and has revealed significant temporal and regional differences.

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Section: Discussionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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