Abstract
The effect of environmental parameters (temperature, salinity and Chl a) upon the condition, reproductive activity and biochemical composition of Crassostrea gigas (Thunberg) in suspended culture in El Grove, Galicia, north-western Spain, was studied over 16 months. Histological study of the gonad revealed two spawning periods. The first spawn took place in June–July, coinciding with the predicted time of ripening. Despite the low water temperature (16°C), a second spawn occurred in October, coinciding with a major phytoplanktonic bloom. Seasonal changes in the main biochemical components of an oyster were computed for a standard animal. Glycogen accumulation was followed by a period of gametogenesis. Lipid biosynthesis during vitellogenesis was associated with glycogen breakdown. High variation in carbohydrate levels during storage and gametogenic development suggests that carbohydrates are the main respiratory substrate. In contrast, proteins and lipids are important for supporting energetic costs during winter when the available food is scarce as indicated by low Chl a levels.
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