Effect of increasing salinity on weight specific filtration rate of juvenile scallops Argopecten purpuratus reared at two temperatures. Is any effect related to ammonia built up?

GASPAR SORIA; GERMÁN MERINO; EDUARDO URIBE; ELISABETH VON BRAND

JOURNAL OF SHELLFISH RESEARCH

NATL SHELLFISHERIES ASSOC

Año: 2011 vol. 30 p. 279 - 286

0730-8000

Argopecten purpuratus (Lamarck, 1819) larvae can be produced in hatcheries within closed aquaculture systems (CAS) and then early-juveniles should be transferred to the sea for further grow-out. A new scallop mass production method from larvae to early-juveniles applying recirculation aquaculture systems (RAS) technology had been developed at Universidad Catolica del Norte. RAS systems might lose water by evaporation, which increases salinity when based upon seawater. 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 16ºC and 22ºC.  Weight specific filtration rates (WFR) 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-hour period had a tendency to be lower at 0-h than at 24-h, for both temperatures; WFRs were higher at 22ºC than at 16 ºC. A significant positive regression was also found between final WFR and TA-N (both NH3-N and NH4+-N) levels. Results presented here should be interpreted with caution outside the shell height range (26.5 ± 1.9 mm).  These results are applicable to the management of A. purpuratus under controlled conditions, such as a RAS.