Assessing the physiological fitness of oysters (Crassostrea virginica) from Eastern New Brunswick, Canada

Abstract

In Atlantic Canada, oyster farmers rely on wild oyster spat collections for their main source of seed. In this study, the physiological fitness of oysters originating from four seed producing areas in eastern New Brunswick (NB) was compared. Oysters [50–70 mm shell height (SH)] from Caraquet, Miramichi, Richibucto and Bouctouche, NB were assessed in a laboratory setting using the following parameters: aerobic capacity (metabolic rate), multi-locus heterozygosity (MLH) and stress response (lysosomal destabilization). Field trials were carried out in different environments in the Richibucto estuary with oysters (∼65 mm SH) from Miramichi and Bouctouche. In the laboratory, significant difference in maximum metabolic rates (VO2max) was found for oysters from Caraquet and Bouctouche, compared to those from Richibuctou. The VO2max were 37 % and 45 % lower in Caraquet and Bouctouche oysters, respectively, compared to those from Richibucto. The Miramichi oysters did not differ significantly from the other oyster populations, including Richibucto (P = 0.063). Significant difference in standard metabolic rates (VO2min) also was found for oysters from Bouctouche, compared to Richibucto. However, aerobic capacity (VO2min:VO2max ratio) did not differ among oyster populations, and no significant difference was found in MLH levels or in lysosomal destabilization indices following the thermal stress event. Field trials (August-November 2012) showed low mortality (0–8%) after ∼100 days, regardless of the sampling period—September vs. November or rearing site—downriver vs. upriver and lysosomal destabilisation indices did not differ between Miramichi and Bouctouche oysters. Results suggest that oysters from the major seed producing areas in eastern New Brunswick (Caraquet, Miramichi, Richibuctou and Bouctouche) are similar in physiological performance and quality.