2007 Fiscal Year Final Research Report Summary
Studies on migration history and population structure of diadromous fish using otolith element and stable isotope signatures
| Project/Area Number |
17380113
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 |
OTAKE Tsuguo The University of Tokyo, Ocean Research Institute, Professor (20160525)
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| Co-Investigator(Kenkyū-buntansha) |
ORIHASHI Yuji The University of Tokyo, Earthquake Research Institute, Assistant Professor (70313046)
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| Project Period (FY) |
2005 – 2007
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| Keywords | otolith / Sr stable isotope ratio / oxygen and carbon isotope ratio / ayu / pink salmon / natal homing / NanoSIMS / microdrilling method |
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| Research Abstract |
The objectives of the study are to examine the migration mechanism and population structure in diadromous fish including ayu (Plecoglossus altiveli) and pink salmon (Onchorhynchus gorbuscha) using otolith element and isotope signatures. 1. Natal homing and migration of ayu: Strontium isotope ratio (87Sr/86Sr) of ayu otolith was found to be identical with the ratio of ambient water, indicating the great potentiality of otolith Sr isotope ratio for revealing natal homing of ayu. We analyzed Sr isotope ratios in otolith core and outer margin, which records the isotope signals of natal and living river water, respectively, with about 5 pm spatial resolution using NanoSIMS. The natal homing of ayu was examined, by comparing isotope ratios of those two otolith portions each other, and only 24% of fish examined was revealed to be a natal homing fish. The ratios of natal homing fish were largely different among rivers (0 to 50%) and were suggested to relate with the current condition of the mouth of natal river. 2. Natal homing and population structure in pink salmon: Otolith oxygen and carbon isotope ratios were found to be different between hatchery and wild juveniles of pink salmon, suggesting that those ratios in otolith to be available to distinguish between homing stocked and wild fish in spawning fish. We sampled otolith core portion of spawning individuals including some stocked fish with thermal scale marking by microdrilling method and analyzed oxygen and carbon isotope ratios. Unfortunately those results were not identical with the ratios of hatchery juveniles. The rearing condition and isotope ratios of rearing water of the hatchery might different from those of the stocked fishes. Contamination of otolith core samples by otolith portion outside of the core might cause the result. Further development of microdrilling method is necessary for such study.
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Research Products
(26 results)
