Lake Biwa is a breeding ground for freshwater fish, including trout, and for the pearl culture industry.

The Lake Biwa Canal, built in the late 1890s and later expanded during the Taishō period, played a role of great importance in the rekindling of Kyoto's industrial life, after a steep decline following the transfer of the capital to Tokyo.

[1][7] The Biwa trout is also endemic to the lake, but some maintain that it is a subspecies of the widespread masu salmon rather than a separate species.

[1][7] The remaining endemic fish are subspecies of Carassius auratus, Cobitis minamorii, Sarcocheilichthys variegatus and Squalidus (chankaensis) biwae.

[8] Recently the biodiversity of the lake has suffered greatly due to the invasion of foreign fish, the black bass and the bluegill.

In July 2009, a largemouth bass weighing 10.12 kg (22 lb 5 oz) was caught from 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.

This indicates that, by this later period, a sophisticated processing technology was mastered in order to remove the harmful tannic acid, and make this food safe for consumption.

It was intended to control the use of synthetic detergents by companies and residents alike and followed a successful citizens' campaign known as the Soap Movement, which had emerged from women's consumer groups earlier in the 1970s.

The legislation established standards for the nitrogen and phosphorus levels for agricultural, industrial, and household water sources emptying into the lake.

At one time there were large areas of reeds along the shores of Lake Biwa, which local government surveys recently found to have halved in size due to encroaching development.