As part of a programme to determine the sampling regime most appropriate for obtaining representative samples from a cultured blue mussel (Mytilus edulis) population, the Fish Health Unit of The Atlantic Veterinary College of the University of Prince Edward Island carried out an extensive field sampling programme at two mussel grow-out sites in Prince Edward Island. The data collected on morphological characteristics, growth rates, and related parameters was examined statistically to determine the nature and extent of variation between sites and among and within individual blocks at each site.

The results indicate that despite the potential for variation as a result of differences in environmental conditions and management procedures, there was little variation between or within blocks at each site. This suggests that, for the time period over which this study was carried out, mussels performed equally well both among and within blocks, and that sampling programmes need not be overly concerned with insuring that samples be taken over a widely distributed area. However, during years of unusually low food quantity or quality, or under conditions of high stocking densities, spatial variations resulting from competition for food resources may be more significant