東日本の海跡湖「北浦」の沖帯における仔稚魚群集の季節変化

抄録

Seasonal patterns of larval and juvenile fish assemblage in a limnetic zone of Lake Kitaura, a shallow large inland-sea lake（7 m maximum depth, 36 km ²）in Ibaraki Prefecture, eastern Japan, were examined by monthly larval net sampling at surface and middle layers from April 2010 to March 2012. A total of 5,272 individuals representing 8 families and 11 species were collected during the study period. Mean numbers of fish species and individuals were more abundant from spring to summer, with non-occurrence in most months during late autumn and winter. The most abundant species were Japanese icefish Salangichthys microdon, pond smelt Hypomesus nipponensis and three gobiids Tridentiger brevispinis, Rhinogobius sp. and Acanthogobius lactipes. Of these, icefish and pond smelt occurred abundantly at both layers in early spring（March and April）, whereas three gobiids at middle layer in most months during late spring and summer（May to September）. Species composition also differed between early spring and late spring to summer. Occurrence patterns and developmental stages of the five abundant species suggested that they would disperse from spawning grounds in littoral habitats and/or inflowing rivers and have more or less different pelagic larval duration and swimming layer in the limnetic zone.