Distribution Pattern and Assessment of an Inversiunio jokohamensis Population at a Reservoir Where Management Was Abandoned

Abstract

The abundance of the freshwater mussel Inversiunio jokohamensis was investigated in a reservoir where management has been abandoned. The investigation was carried out on September 12, 2009, and composition of microalgae investigated on November 8, 2009. The results obtained were summarized as follows: 1) individuals in shore side habitat were more abundant than in offshore side; 2) there was a noticeable absence of individuals with < 50 mm body length; 3) the ratio of old individuals was high while diversity of generation was minimal; 4) no fish were caught using a trap method in the reservoir. This research indicated that recruitment had not occurred for several years.