2007 Fiscal Year Final Research Report Summary
Estimation of juvenile southern bluefin tuna migration using an acoustic telemetry system
| Project/Area Number |
16255010
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 海外学術 |
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| Research Field |
General fisheries
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| Research Institution | Hokkaido University |
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Principal Investigator |
MIYASHITA Kazushi Hokkaido University, Field Center for Northern Biospher, associate professor (70301877)
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| Co-Investigator(Kenkyū-buntansha) |
WATANUKI Yutaka Fisheries Research Agency, National Research lnstitute of Fisheries Engineering, chief scientist (40192819)
高尾 芳三 (独)水産総合研究センター, 水産工学研究所, 室長(研究職) (00372079)
KAWABE Ryo Nagasaki University, Faculty of Fisheries, associate professor (80380830)
WATANUKI Yutaka Hokkaido University, Faculty of Fisheries Science, associate professor (40192819)
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| Project Period (FY) |
2004 – 2006
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| Keywords | outhern bluefin tuna / oded pinger / igration / nnual variability / coustic telemetry |
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| Research Abstract |
In the study period, we made a significant progress on mainly two issues. The summery of results are described below.
1. Environmentally-based distribution
When the influence of the Leeuwin Current was strong (2004-05),warm water (approx. 19.5℃) was widely distributed in the survey area. In this season, many juvenile southern bluefin tuna (SBT) were intensively distributed over the surroundings of inshore seamounts (92% of all appearances).Whereas in 2005-06 when the influence of the current was weak in the survey area, inflow of cold water from sub-Antarctic could be considered, and many warm and cold water masses existed on the continental shelf. Therefore, SBT juveniles were not concentrated near the seamounts, but they tended to occur around the water masses. From the above and past studies, it was suggested that the distribution of SBT juveniles was greatly influenced by the distribution of. Pelagic prey species such as Sardinops sagax and juvenile Scomber australasicus, Which are related to the changes of ocean environment.
2. Size-dependent distribution
In all the years, large SBT tended to be received by coastal receivers. When 2-year-and 1-year-old SBT were simultaneously distributed over the same area (2003-03 and 2003-04), 2-year-olds occurred more inshore, and when 2-year-olds were not distributed (2004-05 and 2005-06), large 1-year-olds (> 50 cm) appeared more inshore than small 1-year-olds (〓 50 cm).Especially in 2004-05, large 1-year-olds concentrated around inshore seamounts (97% of all appearances for large 1-year-olds, small 1-year-olds: 50%).For this reason, it was thought that juvenile SBT were performing size-dependent competition between individuals aiming the niche of the surroundings of inshore seamounts where many preys (Spratelloides robustus, Engraulis australis and etc.) are distributed
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