Temperature and quality of the available food are important factors that in£uence the physiology of oysters; however, the combined e¡ects have not been well studied. We evaluated the impacts of the temperature and diet on the growth, survival and biochemical composition in the Paci¢c oyster Crassostrea gigas spat, cultured in the laboratory for 8 weeks at 23, 26, 29 and 32 1C and fed Isochrysis sp.-Pavlova lutheri (IP) and Dunaliella tertiolecta (Dt). The growth and biochemical composition showed a pattern, which changed in response to rising temperature. The shell length was signi¢cantly longer, in spat fed the IP diet, except at 32 1C, where both diets produced poor growth results. The survival was o50% after 5 weeks at 32 1C, whereas at all other temperatures it was 488%. High temperatures directly increased lipids and saturated fatty acids, while the proteins, carbohydrates and unsaturated fatty acids decreased. High temperatures achieved in the environment, as those reached on clear summer days during low tides, are an important stressor in oyster spat, especially when the quality of the available food is poor.

Survival, growth (length and weight), development, proximate composition, and energy content of Artemia franciscana fed for 7 days with Isochrysis sp. (TISO) or with Chaetoceros muelleri (CHGRA) were compared to evaluate the food value of these microalgae. Mean daily survival was not signi¢cantly different, and ranged from 86% to 93%. Diet-related di¡erences in growth were noted from the third day, and mean ¢nal dry weights (DWs) were 171 and 327 mg ind À1 for Artemia fed TISO and CHGRA respectively. Rates of development were di¡erent between diets, with a higher developmental index for Artemia fed TISO before day 3, and a higher index for Artemia fed CHGRA for the rest of the experiment. Chemical analysis showed that carbohydrates decreased to approximately 35% of the initial value in Artemia during the ¢rst 24 h, after which they remained approximately stable and similar with both diets. In percentage of total DW, lipids and proteins remained close to their respective initial values, but A. franciscana fed TISO had a higher ash content. A major di¡erence between the two microalgae was the higher protein content of TISO, but this did not result in better growth. Of the two, TISO was richer in docosahexaenoic acid, which might explain the initial faster development, but CHGRA was a better source of eicosapentaenoic acid, which is the most probable explanation of the higher food conversion index, speci¢c growth rate, and energy gain of A. franciscana fed this algae. Growth of Artemia franciscana with two microalgae M C Lora-Vilchis et al.At the bottom mean (X), standard error (SEM), mean di¡erence (d AE SEM), and results of Student's t-tests for paired data.Aquaculture Research, 2004 Growth of Artemia franciscana with two microalgae M C Lora-Vilchis et al.

No abstract

The mangrove cockle Anadara grandis (Broderip and Sowerby, 1829) is a potential candidate for aquaculture and for bioremediation of aquaculture effluents in the tropical and subtropical coastal areas of the eastern Pacific Ocean. Laboratory-produced spat are available, but there is no information on their responses to the range of environmental conditions to which they might be subject during the growth cycle. The aim of this study was to evaluate the filtration and clearance rates of A. grandis spat (shell length 9.50±0.37 mm) with a food concentration (7.5 mg�l (7.5 mg�l-1) at four different temperatures (22, 25, 28 and 31 �C, with p�� �� 7.5±0.2 and at four different temperatures (22, 25, 28 and 31 �C, with p�� �� 7.5±0.2 and O 2 concentration of 6.4±0.5 mg�l-1 ; experiment one); and with a temperature (25 �C) and five concentrations of (25 �C) and five concentrations of five concentrations of suspended matter (from 7.5 to 29 mg�l-1 and p�� and O 2 values of 7.9±0.2 and 6.8± 0.4 mg�l-1 ; experiment two). Filtration and clearance rates were highest at 25 �C and significantly different (p<.05) from those obtained at 22, 28 and 31 �C; the clearance rates had the same tendency but the differences were not significant (p >.05). In the second experiment filtration increased according to the amount of food available, but there were no significant differences (p>.05) between 7.5 and 11 mg�l-1 and from 22.4 to 29 mg�l-1. The trend was similar for clearance, and in this case significant differences were found (p<.05) between 7.5, 22.4 and 29 mg�l-1. Filtration at 31 �C was close to 80% at the optimum temperature of 25 �C, which indicates that A. grandis is a good candidate for tropical aquaculture. Clearance increased with high concentrations of suspended solids, but the production of biodeposits could be a source of environmental concern. Therefore, the possibility of using this species for bioremediation of aquaculture effluents should be studied with larger specimens and at higher seston concentrations.

No abstract