UBC Theses and Dissertations
Invertebrate fouling community composition associated with Pacific oyster (Crassostrea gigas) suspended tray culture Switzer, Soleil Elana
Fouling organisms associated with suspended oyster aquaculture can significantly increase operational costs for growers and significantly decrease product marketability. Currently, there is little information available on the fouling communities present on deep-water, suspended tray Pacific oysters (Crassostrea gigas). In general, the industry practice in tray production of Pacific oyster is to use plastic trays, but a new polyvinyl-coated metal tray, which accommodates higher oyster densities, has recently become available. The objectives of this thesis were firstly, to assess whether differences exist in the extent of tray fouling between the 2 tray types using abundance, species richness, biomass, and dominance (univariate analyses) and the Bray-Curtis Dissimilarity Coefficient (multivariate, cluster analysis) as measures (Chapter 2) and secondly, to describe variation in the fouling organisms present on the oysters in the 2 tray types using the same univariate and multivariate analyses (Chapter 3). This study took place on a commercial oyster farm between the months of October 2006 and October 2007. Overall, there was little difference in the extent of fouling communities between the tray types, although a few species were present on plastic trays only, but in very low abundance. The fouling communities associated with the trays and oysters were studied in the winter, spring, summer (tray only) and fall to determine seasonal variation in the fouling communities. Abundance, species richness, biomass and dominance in the tray fouling communities were affected by season with the greatest values in July and the lowest values in January. Season also influenced the oyster fouling communities. Abundance, biomass and dominance of the fouling communities on the oysters was higher in October, while species richness was lowest in January compared to April or October. The seasonal changes observed in the fouling communities on both the trays and oysters were driven largely by a few species. High abundances of Caprella mutica and Mytilus sp. on the trays in July could impact oyster growth through the reduction of water flow through the trays or, in the case of Mytilus sp., through direct competition with the oysters for food and/or space.
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