Research Document - 2015/014
Evaluating transfers of harvested shellfish products, from the west to the east coast of Vancouver Island, as a potential vector for European Green Crab (Carcinus maenas) and other non-indigenous invertebrate species
By Curtis, L. J. F., Curtis, D. L., Matkin, H., Thompson, M., Choi, F., Callow, P., Gillespie, G. E., Therriault, T. W, and Pearce, C. M.
Abstract
The spread of non-indigenous species (NIS), such as the European Green Crab (Carcinus maenas), through human-mediated vectors has become a global concern. The transfer of live seafood and aquaculture products has long been thought to be one of the primary vectors of many well established and notorious NIS around the world. However, there is little to no primary evidence of the potential of this particular vector to entrain and transport NIS to new areas. This has become particularly relevant given the arrival of the European Green Crab on Vancouver Island in the late 1990s as well as the recent transfer of regulatory authority of the aquaculture sector from the provincial government of British Columbia to the Pacific branch of the federal Department of Fisheries and Oceans (DFO Pacific) and the continued growth of shellfish aquaculture in British Columbia. In 2010, Aquaculture Management at DFO Pacific thus became concerned about this vector, particularly with regard to the European Green Crab, and developed Conditions of License as a precautionary approach to reduce the risk of NIS transfer to new areas. In 2011, Aquaculture Management requested scientific advice on these license conditions, which led to a multi-faceted project that investigated the NIS entrainment potential of shellfish transfers, and reviewed potential mitigation measures and current licensing conditions.
The potential for NIS entrainment on shellfish was investigated through a long-term experimental study carried out along the west coast of Vancouver Island in waters that were known to be infested with European Green Crab. Mid-way through the experimental study, a short-term observational study was also conducted using shellfish product as it arrived at processing facilities. The entrainment potential of six NIS on shellfish was investigated and was confirmed for the European Green Crab at two different life stages and four other NIS. Five NIS, not including the Green Crab, were also found on shellfish products that had been transported to processing facilities. They included three well known NIS tunicate species as well as two non-indigenous bryozoans. After an extensive review of the literature, we confirmed that none of the existing or experimentally tested mitigation methods to remove NIS from products was 100% effective at removing NIS prior to product transport. We also identified several areas of potential improvement of the current shellfish aquaculture license conditions which culminated in the development of a conceptual framework model to reduce the risk of spreading NIS at each stage of the shellfish transfer process.
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