Effect of increasing salinity on weight-specific filtration rate of juvenile scallop Argopecten purpuratus reared at two temperatures: Is any effect related to ammonia buildup?

Abstract

Larvae of the northern Chilean scallop Argopecten purpuratus (Lamarck, 1819) can be produced in hatcheries in closed aquaculture systems (CAS), and then early juveniles transferred to the sea for further grow-out. A new scallop mass production method from larvae to early juveniles that applies recirculation aquaculture system (RAS) technology has been developed at Universidad Catolica del Norte. RASs might lose water by evaporation, which increases salinity. Water temperature will increase as well if it is not controlled. An experiment was performed to determine the effect of varying salinity and temperature over water quality parameters and scallop physiological processes. Feeding behavior of A. purpuratus was determined under CAS with daily water exchange for hatchery-produced juvenile scallops (mean shell height, 26.5 mm; SD, 1.9) reared at salinities of 34, 38, and 42 g/L, and temperatures at 16°C and 22°C. Weight-specific filtration rates (WFRs) were analyzed at day 12 and again at day 55. Scallops were fed Isochrysis galbana and Chaetoceros calcitrans (ratio, 1:1). Results shows that WFRs analyzed for a 24 h period had a tendency to be lower at 0 h than at 24 h, for both temperatures; WFRs were higher at 22°C than at 16°C. A significant positive regression was also found between final WFR and total ammonia nitrogen (both NH3-N and NH4 +-N) levels. Results presented here should be interpreted with caution outside the shell height range of 26.5 ± 1.9 mm. These results are applicable to the management of A. purpuratus under controlled conditions, such as a RAS.