In this study, the feasibility of identification and abundance estimation of isada krill, Euphausia pacifica, was examined using a two‐frequency (38 and 120 kHz) method. The acoustic survey and midwater trawling were conducted off the Sanriku coast, northern part of Honshu, Japan. In one pattern, the SV difference between the two frequencies was large, and in the other, the SV difference was small. These results were interpreted by scattering models, and showed that discrimination between isada krill and walleye pollock was possible.

A new species of pit crab of the genus Fizesereneia Takeda & Tamura, 1980, Fizesereneia daidai sp. nov., is described and illustrated based on specimens collected from the scleractinian corals Micromussa amakusensis and Micromussa sp. in Japan. The new species, the sixth assigned to the genus, can be separated from its congeners by having an orange posterior carapace in life, a subrectangular carapace, the width to length ratio of the carapace depressions being approximately three-halves, the midline of the carapace depression being almost invisible in lateral view, and the ocular peduncles being mostly exposed. The usefulness of the fusion or separation of the pterygostomial region to the carapace as a generic character is discussed.