Macrobenthic fauna and its historical changes in brackish Lake Obuchi Aomori Prefecture, Japan

Abstract

The macrobenthic fauna in brackish Lake Obuchi (halfway down the Shimokita Peninsula in Aomori Prefecture), were observed at eight locations from 2001 to 2003. Individual densities of macrobenthos at the mouth of the freshwater river and the lakeshore were comparatively higher than those at the center of the lake. Of the 53 species found in this survey, most were of the taxa Mollusca, Annelida and Arthropoda. The dominant species were Prionospio (Minuspio) japonica, Polydora sp., Iravadia (Fluviocingula) elegantula, Musculus senhousia, Macoma takahokoensis and Gnorimosphaeroma oregonensis. Although the species composition and its number of the benthos in Lake Obuchi were similar to those of 50 years ago, the increase in Capitella capitata, Myitilus galloprovincialis and Mya (Arenomya) arenaria oonogai were only recently confirmed.