人造湖におけるイワナSalvelinus leucomaenisの生活史変異とその分岐

概要

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In order to clarify the variation of the life-history of Japanese charr Salvelinus leucomaenis inhabiting an artificial lake constructed by damming, their growth, maturity, reproductive chracteristics and down-migration pattern in the lake-inlet stream system were studied. Two types of mature fish in both male and female, stream residents and migrants, which were distinguishable by body size, coloration and secondary sexual characters were recognized. From analysis of their otolith radius length, migrants appeared to grow more rapidly than residents after 0+ of age. Females in both types matured from 2+ of age, but stream resident males were more precocious (from 1+) than migrants (from 2+). Juvenile fish which were mainly 0+ and fairly 1+, migrated down from inlet stream to the lake. Down-migration occurred nocturnally from May to october with a peak in May. The body length of migratory fish of 0+ was significantly shorter than that of resident fish in May and August, but no differences in the body length were observed in other months. Possible mechanisms as causes of different life-history patterns were discussed.
日本生態学会の論文
1992-08-10