Lake Biwa - Natural History

Natural History

Lake Biwa is of tectonic origin and is one of the world's twenty oldest lakes, dating to almost 4 million years ago. This long uninterrupted age has allowed for a notably diverse ecosystem to evolve in the lake. Naturalists have documented about 1100 species in the lake, including 58 endemic species. Among these endemics are four fish species: Gnathopogon caerulescens (a cyprinid), Opsariichthys uncirostris (a cyprinid), Gymnogobius isaza (a goby), and Silurus biwaensis (a large silurid catfish). Lake Biwa is also an important place for water birds. About 5,000 water birds visit Lake Biwa every year.

Recently the biodiversity of the lake has suffered greatly due to the invasion of foreign fish, the black bass and the bluegill. Bluegill were presented to the Emperor and later freed in the lake as a food source for other fish. Black bass were introduced as a sport fish. In July 2009 a largemouth bass weighing 22 pounds, 4 ounces was caught in the lake by Manabu Kurita. It has been officially certified by the International Game Fish Association (IGFA) to tie the largemouth bass world record held solely by George Perry for 77 years.