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

Abstract

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 (Saricay 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 Saricay 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 per mil. Increase in mussel weight was highest at the second station (19.29%) with a moderate salinity (1.5 per mil), while that with a growth loss was observed at the third station (-1.56%) with the highest salinity concentration (3 per mil). 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 per mil) and fifth stations (salinity 6 per mil) at the end of the experiment.