2012 Fiscal Year Final Research Report

Reexamination of migration patterns of masu salmon Oncorhynchus masou inferredfrom new otolith techniques

Research Project

Project/Area Number	22780173
Research Category	Grant-in-Aid for Young Scientists (B)
Allocation Type	Single-year Grants
Research Field	General fisheries
Research Institution	The University of Tokyo
Principal Investigator	KUROKI Mari 東京大学, 総合研究博物館, 助教 (00568800)
Project Period (FY)	2010 – 2012
Keywords	初期生活史 / 回遊生態
Research Abstract	The habitat shifts of the juvenile of masu salmon, Oncorhynchus masou, were studied at four streams in Hokkaido. Otolith Sr:Ca ratios of smolts in the Betsubetsu, Ninaibetsu and Moshosanbetsu rivers, showed low values, suggesting that these fishes remained in freshwater habitat until the smolt stage, while the ratios of the smolts in the Tokotan River increased after the fry stage suggesting that they might have experienced the brackish water habitat. A similar pattern was observed in all of the three years studied. The Tokotan River is the steepest and the stream width is narrow causing rapid flow, although the annual water temperature of the Tokotan River is intermediate among streams studied. These results suggest that the topography and resultant flow conditions may influence the habitat shifts of masu salmon, and the juveniles in the Tokotan River may be flushed out of the river with the strong flows from melted snow in early spring.