諏訪湖におけるワカサギ稚魚の生態について : 付.諏訪湖の富栄養化の進行とワカサギ漁獲量の関係

概要

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Newly hatched larvae of the pond smelt tend to be distributed in the deeper layer of the profoundal region of Lake Suwa, probably after being carried by the inflow of the river where the hatchery is located. They begin to migrate with growth towards the sublittoral region. The succession of food organisms eaten by the larval and young pond smelts in the lake can be indicated as follows : rotifers (pro-larva and early post-larva)→copepod nauplii (early post-larva)→Bomsina and Mesocyclops (post-larva and young fish)→Leptodora and Diaphanosoma (young fish). Observations of cultured larvae in a glass aquarium showed that the larvae up to a body length of 11 mm or more caught their food by a darting movement produced by a S-shaped flexure of the body and those up to 16 mm or more swam in one or more schools gathering each other. In appendix, the relation of the progress of eutrophication in the lake to the annual catches of the pond smelt in the course of the recent thirteen years is discussed.
1974-03-30