Declining freshwater mussel diversity in the middle and lower reaches of the Xin River Basin: Threat and Conservation

Freshwater mussels provide important functions and services for aquatic
ecosystems, but populations of many species have been extirpated.
Information on biodiversity plays an important role in the conservation
and management of freshwater mussels. The Xin River Basin is a
biodiversity hotspot for freshwater mussels in China, with more than 43
species known, but populations of which are decreasing. Here, we quantify
the diversity of freshwater mussels in the middle and lower reaches of the
Xin River Basin and study the correlation of habitat characteristics and
freshwater mussel diversity. Compared to the historical period, the number
of species, density and biomass of freshwater mussels decreased 33%, 83%
and 82% in the current period, respectively. 52% of recorded species were
empty shells, and 14 native freshwater mussels were not found in the study
area. Four species are currently listed as vulnerable species using IUCN
criteria and their global status. The assemblage structure of freshwater
mussels exhibits significant spatial differences, and there was a
correlation with substrate and physicochemical parameters. The main
tributary of the Xin River with higher freshwater mussel diversity should
be established as one large protected area because the nestedness
component was the main pattern of beta diversity. These results indicated
freshwater mussel diversity was declining rapidly, which can help focus
conservation effort for freshwater mussel biodiversity.