Salinity tolerance of juvenile scallops ( Pecten maximus L.) at low temperature

Abstract

The effects of reduced salinity on survival, filtration rate and behaviour of juvenile scallops ( Pecten maximus) were studied at 5.0°C and 9.4°C. Daily observations of mortality and behaviour, and weekly measurements of filtration were made for 30 days at the original salinity of 33 ppt, and at reduced salinities (29, 26, 23, 20 ppt, and weekly fluctuating between 27 and 29 ppt) and thereafter for a 15-day recovery period at the original salinity. The results show that there was no mortality in scallops at 9°C at salinities above 20 ppt and only low mortality at 20 ppt, while the scallops at 5°C had high mortality (> 50%) at salinities lower than 26 ppt. The filtration rate showed little variation between salinities above 20 ppt at 9°C, and between salinities at 5°C and 20 ppt at 9°C. The filtration rate in salinities over 20 ppt at 9°C was 4–5 times higher than at 5°C. The scallops responded to reduced temperature and salinity by retracting tentacles and mantle edge or closing valves. It is recommended that scallop farms in western Norway should be located in areas where salinity seldom drops below 29 ppt.