河口汽水域におけるイサザアミ属（Neomysis） 2種の鉛直分布の日周変化

抄録

In order to reveal vertical distribution patterns of two mysid species, Neomysis, we collected the mysids from surface, middle and bottom layers in Hiroura Lagoon located in the estuary of Natori River, twice in spring and neap tides, 1994. N. awatschensis and N. japonica coexisted in the lagoon. Although both species distributed mainly in the bottom layer, they occurred in the surface and middle layers in night time. Through correlation analysis, negative effect of illuminance on the density of mysids was found. Their distributions would be expanded to the surface due to their swimming activities enhanced in night. Relationship of stomach fullness and maturational condition with the diel vertical distribution of N. japonica was not significant; however, juvenile N. awatschensis and the mysid without full stomach contents tended to distribute in the middle and surface layers. N. japonica often disappeared from the bottom layer, while N. awatschensis stayed there almost all the time. Behavioral differences were shown between these species.