Deepest demersal fish community in the Sea of Japan : A review

Abstract

Deep sea demersal fish community in the Sea of Japan was reviewed chiefly on the basis of Kaiyo-Maru collections in 1970 along with other data available for the depth ranges until ca. 2000 m. From relationships of species richness with depth in relation to peculiar hydrographic conditions of the Sea, fish species found below a depth of 500 m was tentatively defined as true deep sea forms. Of a total of 20 species from 7 families of this fauna usually having eurybathic distribution, only 6 species referable to the secondary deep sea fishes inhabit the bottom deeper than 1000 m. Until a depth of 2000 m, they disappear from this community with increasing depths in the order of Aptocyclus ventricosus, Bathyraja smirnovi, Careproctus trachysoma, Petroschmidtia toyamensis, Malacocottus gibber and Bothrocara hollandi. Biological aspects of main species, particularly of B. hollandi, are described with special references to bathymetric series of size frequency and reproductive characters, besides several systematic annotations including the presence of two morphotypes in B. hollandi. In general, there are 'smaller-deeper trend' in these fauna except M. gibber. They also shared moderately to very low fecundity coupled with moderate to extremely egg sizes in common. Based on the stomach content analysis and feeding types, their food web interactions were outlined, suggesting a relatively well balanced community structure largely depending on the pelagic prey animals at least above a depth of 1000 m. It is concluded that so-called "taraba-community III" represents the deepest demersal fish community in this sea, whereas its fauna and structure changes remarkably with depth, finally monopolized by B. hollandi until at least a depth of about 2000 m.