Influence of channeling by conduit pipes on the fish and crustacean assemblage in the enclosed Honjo Area of Lake Nakaumi

Abstract

A one year experiment was carried out from March 1998 by the Ministry of Agriculture, Forestry and Fishery to estimate the fishery utilization of the Honjo Area isolated from Lake Nakaumi for land reclamation. It was intended to reveal the influence on the fish assemblage in the Honjo Area by channeling with two conduit pipes between the Honjo Area and the northern drainage channel. We compared the seasonal fish catch during the experimental year with the previous years catch not only in the Honjo Area but also in Lake Nakaumi, especially at the western end of the lake. Two years before and after construction of the water way, there was no remarkable difference in the migration patterns of Metapenaeus ensis and marine species, which usually migrated from Sakai Channel to the Honjo Area via the western drainage channel. Therefore, it was considered that such fish and crustaceans did not migrate directly from Sakai Channel to the Honjo Area through pipes in the northern drainage channel. Based on the fish migration data, a more appropriate method of enlarging the excavation and replacing the point was proposed for the purpose of this experiment.