For P. maximus, salinity less than 28 psu resulted in significantly lower growth rates at 13–21 C (Table 1) suggesting that sites where this salinity might occur regularly should be avoided. A similar conclusion was reached by Strand et al. (1993) as they found that tolerance to low salinity, measured as mortality and filtration rate, in 30-mm shell height animals, was reduced at low temperature (5 C). At 9 C, the lowest temperature used in these experiments, salinity of 26 psu also resulted in lower growth than at 30 psu although at this temperature, growth rate was low in all treatments and the difference was not significant.