Estimation of total species richness of the freshwater mollusks of the middle and Lower Volga

Freshwater mollusks species richness has been analyzed on materials collection in 2012-2014. At total, 113 species were found. Species accumulation curves show incomplete registered species richness of the region. The statistical assessment of the estimators results accuracy of optimal ratio between minimal sampling efforts (60) and maximal information about mollusk (70%) species richness at the region. It was shown, all estimators give overestimated results of the accumulation curves. Magnitude of resulted by estimator Bootstrep, displayed the most similar values to the really observed species number.