| Project/Area Number |
11660174
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | Hokkaido University |
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Principal Investigator |
TAKAGI Shogo Hokkaido Univ., Fac. of Fis., Lec., 水産学部, 講師 (60179421)
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| Co-Investigator(Kenkyū-buntansha) |
KAERIYAMA Masahide Hokkaido Tokai Univ., Fac. of Eng., Prof., 工学部, 教授 (80305937)
ISODA Yutaka Hokkaido Univ., Grad. School of Fis., Asso. Prof., 大学院・水産科学研究科, 助教授 (10193393)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2000: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1999: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | Oncorhynchus / Gonatidae / Golf of Alaska / Ridge Domain / Oncorynchus / Gnnatidae / Galf of Alaska / Oncorhynshus |
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| Research Abstract |
The feeding ecology of pacific salmon (Oncorhyncus) in the Golf of Alaska was investigated during early summers of 1994-2001. The dominant prey of salmon were squids (mainly Berryteuthis anonychus) in the Subarctic Current, and zooplankton (e.g., euphausiids, copepods, and pteropods) in the Alaskan Gyre during 1994-1996 and 1998. Food competition occurred between sockeye and pink salmon. Pink salmon appeared to feed on more diverse prey at a lower tropic level than sockeye salmon. The feeding and growth of sockeye and pink salmon were affected by the El Nino event during spring and summer of 1997.
Analysis of δ 13C and δ 15N isotope values and stomach contents of Pacific salmon indicate their summer feeding ecology and tropic dynamics have changed in the offshore waters of the Golf of Alaska since the 1990s. Scatter plots in the δ 13C - δ15N plane of Pacific salmon in 1999-2000 showed that the difference in isotope values was generally consistent with stomach content analyzes, i.e., Chinook salmon, steelhead trout, coho salmon, sockeye salmon, pink salmon, and shum salmon in order of tropic level. Our results suggest that sockeye, pink, and chum salmon show a high plasticity in their feeding strategy such as switching diets from micronekton or jellyfish to zooplankton according to changes in the ecosystem.
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