1998 Fiscal Year Final Research Report Summary
Reproduction of Japanese anchovy in the Kuroshio Extension and transition waters.
| Project/Area Number |
09660195
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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 | The University of Tokyo |
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Principal Investigator |
AOKI Ichiro The University of Tokyo, Gradate School Agricultural and Life Sciences, Assistant Professor, 大学院・農学生命科学研究科, 助教授 (40114350)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUSHITA Katsumi The University of Tokyo, Gradate School Agricultural and Life Sciences, Assistan, 大学院・農学生命科学研究科, 助手 (00012039)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Japanese anchovy / Spawning / Fish larvae / Growth / Kuroshio Extension / Transition region |
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| Research Abstract |
Spawning frequency, which is represented by the fraction of females with postovulatory follicles, and batch fecundity were higher in offshore populations than in coastal ones. This suggests that anchovy in offshore waters adopt a reproductive strategy in which they assign more energy to reproduction and produce more eggs in a certain period than those in coastal waters. Anchovy spawn in the temperature range of 8-22ﾟC with batch fecundity varied in proportion to temperature. This enables anchovy to utilize offshore extensive areas as their spawning grounds. On the other hand, the analysis of mtDNA showed that several anchovy populations off the coasts
from northern and western Kyushu to Honshu-Hokkaido were not distinguished genetically.
Anchovy larvae and juveniles were distributed widely as far offshore as 160 deg.E.They migrated offshore, growing at a rate similar to those in coastal waters. The daily mortality rate decreased with growth, being lowest for larger Jarvae offshore. Stomach content analysis revealed that occurrence of empty stomach was very high in larvae <30mm SL and reduced for juveniles> 35mm SL.Food organisms were predominated by copepods. With increase in fish size, occurrence of warm water species of copepods and amphipods increased. It was suggested that juveniles > 55mm SL feed on conspecific small larvae.
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