Abstract

Adult Argopecten purpuratus were conditioned under four different temperature regimes and their gonadal development and quality of the resulting offspring evaluated. Biochemical composition of muscle and gonad, during laboratory conditioning at the different treatments, was also examined. Spawned-out individuals were obtained from commercial culture centers for experimentation. Test groups of scallops were independently maintained at: (a) 15°C, (b) 19°C, (c) 15°C in the first stage, raised to 19°C in the second stage, and (d) 19°C in the first stage decreasing to 15°C in the second stage. Scallops were maintained in seawater which was changed daily, provided with aeration, and were continuously fed a diet consisting of 50% Isochrysis galbana (var. T-iso) and 50% Chaetoceros gracilis. The daily ration was equivalent to 6% of the dry biomass of the scallops. Animals were maintained under a constant photoperiod of 12-h light and 12-h dark. Progress of gonadal recovery was followed by periodic determination of gonadosomatic index (GSI) and histological analysis. The highest percentage of scallops attaining spawning condition and highest values for GSI was obtained from animals conditioned under the constant 15°C regime. The group started at 15°C and raised to 19°C showed the most variable pattern of maturation. Of the major biochemical components of the adductor muscle, lipids and proteins changed most during conditioning under any of the temperature regimes; changes in carbohydrate levels in this tissue were only detected for scallops maintained at a constant temperature. Changes in protein levels, depending on the time and temperature of conditioning, were detected in the gonad. Based on quality indicators used in this study, including fecundity, egg size, biochemical composition, and "D" larvae survival, the best physiological conditioning for the reproductive process was obtained in scallops, which were conditioned at a constant temperature of 15°C, and at an initial temperature of 19°C and then decreased to 15°C. Results showed an inverse relationship between temperature and conditioning success and the importance of maintaining stable temperatures during the laboratory conditioning process which permitted adequate accumulation and use of nutritional reserves required to produce highly viable larvae. © 2003 Elsevier Science B.V. All rights reserved.