Endemic gastropod distribution in Baikal

A peak in overall gastropod diversity (80 of the 117 endemics species) was observed at a depth 5–20 m. About 30 species live deeper than the photic zone which is about 100 m in Baikal, but their reproductive areas are located at a depth 15–50 m. Only 10 are true deep-dwelling (>100v) species. Twelve gastropod species occur at different depth in all three basins of the lake. Species distribution varies considerably; some are linearly fragmented, many species have patchy distribution, and several have been found in many points in the lake. On the basis of statistical analysis of endemic gastropod occurrences in different regions, it is suggested that Baikal should be divided into two provinces: Northern Baikal (Northern basin, Maloe More Strait, Ushkany Islands, Chivyrkuy Bay) and Southern Baikal (Southern and Middle basins). It appears these Baikal provinces bear some similarities to bivariate distributional provinces of the Pacific Ocean.