Comparative analysis of oxygen consumption rates between cupped oyster spat of Crassostrea gigas of French, Japanese, Spanish and Taiwanese origins

Respiration rates of various geographical strains of Crassostrea gigas were compared to assess the respiratory expenditure as a physiological indicato r of catabolism (cost of maintenance). Parental oysters, sampled in France (Marennes-Oleron), Japan (Hiroshima), Taiwan (Tunkang) and Spain (Cadix), w ere differentiated by both their geographic origin and by mitochondrial DNA markers, allowing the distinction between the two closely related taxa Cra ssostrea gigas and Crassostrea angulata. After reproduction of these parent al oysters, respiration rates of spat of each strain, reared under common c ontrolled conditions, were individually estimated at 20 degrees C by using a volumetric microrespirometer. Our results demonstrated that physiological variability existed among the Crassostrea gigas strains and is likely to b e related to physiological differences between geographical regions and/or genetic adaptations. The French strain showed the highest rates (0.71 mu L. h(-1)), while the Japanese, Taiwanese and the hybrid between Spanish and Fr ench strains consumed less, 0.53, 0.43 and 0.40 mu L.h(-1) respectively. Ou r results confirmed the discrepancies previously suggested between Crassost rea gigas and Crassostrea angulata. Comprehensive physiological assessments should be carried out over a wide temperature range to confirm our results and to further evaluate growth potential. Appropriate decision making base d on these studies will help future shellfish management in shellfish reari ng areas such as the overstocked Marennes-Oleron Bay. (C) 1999 Ifremer/Cnrs /Inra/Ird/Cemagref/Editions scientifiques et medicales Elsevier SAS.