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

在北海道的四条河流中，研究了马苏鲑幼鱼的栖息地迁移。北别江、尼内别江和莫舍山别江幼鱼的耳石Sr:Ca比值较低，表明这些幼鱼在幼鱼期之前一直处于淡水栖息地，而东滩河幼鱼的耳石Sr:Ca比值在幼鱼期之后有所增加，表明它们可能经历了咸淡水栖息地。在所有三年的研究中都观察到类似的模式。虽然土滩河的年水温在所研究的河流中处于中间水平，但它是最陡峭的河流，河流宽度窄，导致水流迅速。这些结果表明，地形和由此产生的水流条件可能会影响鲑鱼的栖息地转移，并且在早春，Tokotan河中的幼鱼可能会被强烈的融雪水流冲出河中。

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.