Distribution and abundance of hyperbenthic mysids in the inner and central parts of Ariake Sound, western Kyushu, Japan

Abstract

Ariake Sound is a highly productive area and a good nursery for fish and shellfish species. Mysids are essential prey organisms for a number of juvenile fishes in Ariake Sound, but their distribution and abundance are not well understood. To investigate species composition and distribution, we collected hyperbenthic mysids with a sledge-net in the inner and central parts of Ariake Sound from 2001 to 2004. Fifteen species of mysid from nine genera were recorded. The numerically dominant species were Orientomysis tenuicauda, Erythrops minuta, Orientomysis aspera, Neomysis japonica, Rhopalophthalmus orientalis, and Hyperacanthomysis longirostris in order. Of these, O. tenuicauda and E. minuta were mainly collected at offshore stations with relatively high salinity. In contrast, the majority of O. aspera and the other three species were collected from nearshore stations and/or river estuaries. The highest density, 7,236 indiv./m², was recorded for O. tenuicauda at a station with a sandy bottom at 20 m depth. Mean estimated density, 241 indiv./m², was low compared with mysid densities recorded in other Japanese estuaries, but exceeded the density, 100 indiv./m², known to maintain the maximum juvenile Japanese flounder growth rate in their nursery ground.