Title Countermeasures against Alien Fishes (Largemouth Bass and Bluegill) in Lake Biwa
Authers Atsuhiko IDE and Shinsuke SEKI
Keywords Lake Biwa, Alien fish, Largemouth bass, Bluegill
Citation Bull. Fish. Res. Agen. No.29, 79-84, 2010
Lake Biwa is one of the world's most ancient lakes, with an origin going back four million years. Many aquatic organisms, including more than 30 endemic species or subspecies of fish and molluscs inhabit the lake, and various kinds of fisheries have targeted those animals for centuries. Bluegill (Lepomis macrochirus) and largemouth bass (Micropterus salmoides) were first found in Lake Biwa in 1965 and 1974. While bluegill spread gradually through the shallow water zones and into small lagoons surrounding the lake, largemouth bass increased explosively in the 1980s. Simultaneously, native fishes such as crucian carp and bitterlings disappeared from the coastal shallows. After that, the population of bluegill began to increase.
 In recent years, bluegill has comprised over 90% of the fish fauna in Lake Biwa's south basin. Since 1985, fishermen have been trying continuously to reduce these alien species by several means. Fishing gear such as Eri (a set-net), gill nets, and pulling nets have been used. Recently, over 400 metric tons per year of these alien fishes have been eliminated. At the same time, the Shiga Prefectural Fisheries Experimental Station has tried to develop more effective gear to catch them. We have devised a pot trap, with its top covered by a sheet to provide shade, for efficient capture of the alien fishes, and a small beam trawl for use in beds of submerged aquatic vegetation. Other methods for the eradication of the alien fishes are currently under study.
URI http://www.fra.affrc.go.jp/bulletin/bull/bull29/9.pdf