サケの稚魚期から幼魚期への発育段階における形態的,生態的特徴

概要

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Juvenlie of different stages (alevin, fry and fingerling) of chum aslmon Oncorhynchus keta derived from natrual spawning and artificial propagation were captured in the Koizumi River and the Futamata River from January to June in 1980, and phasic development from fry to fingerling was examined. The phasic changes in morphology, growth mode, behavior and ecology were observed when the juvenlie grew to 4.1-6.0cm in fork length. Namely, 1) squamation was intiated at 4.1-5.0cm, 2) the specific growth rate maximized at about 5.0cm, 3) the condition factor became stable at about 9 after the juvenile grew up to 5.1-5.5cm, 4) parabolic curves indicating the relationships between ratios of head length (HL), body depth (BD) and upper jaw length (UJL) to fork length (FL) and fork length inflected at 5.3cm for HL/FL, 5.9cm for BD/FL and 5.4cm for UJL/FL, 5) most of fish migrated seaward at 4.1-6.0cm, 6) juvenile larger than 5.5cm changed their life space from pools to rapids of the rivers. Among these changes, the squamation is the most practical criterion of the phasic change from fry to fingerling.
日本水産學會の論文