Temporal and spacial distributions of macrobenthos in Mutsu Bay.

概要

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In order to elucidate the conditions of food environments for righteye flounders Limanda herzensteini and L. yokohamae in Mutsu Bay, Aomori Prefecture, the distributions of macrobenthos were investigated by analyzing grab samples obtained at approximately 300 stations chiefly from March 1980 to February 1983. Faunal composition in the bay was correlated with the mud contents in the bottom sediments. In the extensive mud bottom in offshore area polychaete annelids predominated, representing 82.8% of the total number of macrofauna. Most of the dominant species, Scalibregma inflatum, Paraprionospio pinnata, and Maldane sarsi, were chiefly abundant in East Bay. So macrofaunal biomass and density in West Bay were consistently lower than those in East Bay. The densities of S. inflatum and Ampharete sp. increased remarkably in spring and decreased in autumn and winter, while no seasonal periodicity was found in fluctuations in den-cities of Lumbrineridae and M. sarsi. There is a general tendency that the macrofaunal biomass in offshore area attains peak in summer and lowest in winter. But such a periodicity was not found in East Bay since the autumn of 1980 because of remarkable increase in density of M. sarsi. Results of cluster analysis showed that the community structure of macrofauna in offshore area varied largely with fluctuations in abundance of dominant polychaetes by seasons and years.