Effect of Salinity on the Growth and Survival of the Freshwater Mussel, Unio crassus, in an Environmentally Disturbed River

The aim of this study was to examine the effects of salinity on the survival and growth of a freshwater mussel Unio crassus, from a Mediterranean stream (Sarıçay Stream) in south-west Anatolia, Turkey, which has highly variable environmental conditions and a salinity gradient. A total of 250 similarly-sized U. crassus were collected from a stream in the species’ native range and transferred in ice to Sarıçay Stream. The length, width, height and weight of each individual were measured before and after the sampling period, a period of 286 days. Significant increases were detected in the height, width and weight of mussels at all sampling points during the study, with the exception of weight in the sampling station third with salinity of 3‰. Increase in mussel weight was highest at the second station (19.29%) with a moderate salinity (1.5‰), while that with a growth loss was observed at the third station (-1.56%) with the highest salinity concentration (3‰). Survival rates over the duration of the study were 60%, 56%, and 66% at stations 1-3, respectively. All mussels were dead at the fourth (salinity 4.5‰) and fifth stations (salinity 6‰) at the end of the experiment.