Constraints to Crassostrea ariakensis aquaculture: Season and method of culture strongly influence success of grow-out

The proposed introduction of the nonnative Suminoe oyster Crassostrea ariakensis to the east coast of the United States to restore the wild oyster fishery and/or for commercial aquaculture is contingent on perceived benefits outweighing costs. Trials conducted at six sites distributed across North Carolina evaluated the likely biologic success of aquaculture of C. ariakensis by assessing the oyster's growth, mortality and fouling under alternative methods and seasons of deployment. Of the six sites at which oysters were deployed, growth of C. ariakensis was greatest at the high-salinity sites, Hoop Pole Creek (29-32 ppt) and Newport River (25-30 ppt) and lowest at the low-salinity site, Nags Head (4 ppt). Across sites, growth was consistently lower (by 50%) in suspended floats than in fixed racks held 15 cm off the bottom. Only on the muddiest sediments (Newport River), where growth in tissue mass was 50% greater and growth in shell mass 20% greater on raised than bottom racks, did growth differ detectibly with rack elevation. In spite of low mortality and fouling over winter, predation in summer by blue crabs resulted in mortality approaching 50% at one of the sites (Swan Quarter) and heavy settlement by Polydora spp. produced a greater than 25% cover of mud-blisters on 84% to 97% of oysters. Consequently suitability of C. ariakensis for sale on the high-valued half-shell market may be contingent on completion of grow-out before summer Polydora spp. infestation. Results indicate that whereas at high salinity sites grow-out from a 27-mm deployment size is typically achieved within 5 mo, at medium salinity sites >7 mo is required. Failure to remove oysters at medium salinity sites from the water prior to summer may result in heavy Polydora spp. infestations that necessitate sale on the lower-valued shucked market. Irrespective of target market, it is recommended that C. ariakensis be grown in fixed racks as opposed to floating structures to maximize rates of growth without compromising survivorship.12 page(s