Sublethal responses of four commercially important bivalves to low salinity

•Response of bivalves differed depending on intensity of salinity stress and season.•Salinity ≤15 caused sharp decrease in SFG and activity (valve closure, burrowing).•For salinities ≥20 diverse responses among species as low activity or compensation.•SFG was an useful indicator to assess salinity stress in adult bivalves.