Escapes and Introductions
Most global scallop aquaculture does not rely on hatchery seed but on wild spat collection and this should be from abundant, well-regulated natural sources. In countries where natural spatfall is poor, or in the case of introduced scallops, spat can be hatchery reared. Hatchery produced spat is increasing being seen as a way to reliably secure quality seed for on-growing.
As many farmed scallops are cultured in their native ranges and are wild-caught or one generation hatchery-raised, there is little evidence to support negative effects on ecosystems or wild populations1. In the early development of scallop farming non-native scallops were introduced to some producer countries, for instance the Bay scallop (native to the Americas) was intentionally introduced to Asia, however no effects on ecosystems or native species have been reported1. It is likely that further non-native species will be trailed and grown in countries outside their native range2.
The movement of scallop seed, stock and equipment could potentially introduce or transfer diseases and pests which can affect farmed scallops or native scallop species4, 5, and high-density cultivation can promote the incidence and spread of parasites and disease6.
The introduction of non-native bivalve species for aquaculture purposes is now highly regulated helping to reduce the introduction of diseases and pests. Internationally the “Code of Practice on the Introductions and Transfers of Marine Organisms 2005”7 has been adopted by many countries, whilst in the EU international shellfish trade has been regulated for many years8. Upcoming European legislation will further prioritise the prevention and control of biological invasions9.
Biosecurity measures are important to mitigate diseases that can affect scallops10. Key elements of biosecurity include; practical and appropriate legislative controls, adequate diagnostic and detection methods for infectious diseases, disinfection and pathogen eradication methods, reliable high quality sources of stock, and best management practices11, 12 Preventive regulatory measures aim to limit imports only from countries where no outbreak of disease occurs13. It is also critical that scallop hatcheries implement strict biosecurity plans to help prevent transfer of disease into, within and from their facilities.
Transfers of spat from hatcheries to on-growing areas, or the relaying of bivalves between sites must be carried out in ways that minimise the risk of disease transfer10, and the monitoring of scallop populations as well as parasite occurrence/levels is important. Management measures include regulation (e.g. lease conditions and permit requirements) but also the use of voluntary agreements, Codes of Good Practice and certification.
Also important are designations to protect sensitive marine habitats. For example in the UK these include Marine Protected Areas (MPAs), Special Areas of Conservation (SACs), Special Protected Areas (SPAs), and intertidal areas identified as Sites of Special Scientific Interest (SSSIs)14.
- Seafood Watch
- Wang, C. et al, 2011. Introduction of the Peruvian scallop and its hybridization with the bay scallop in China. Aquaculture, 310(3) p380-387
- McKindsey, C. W. et al, 2006. Effects of shellfish aquaculture on fish habitat. Fisheries and Oceans
- Brenner, M. et al, 2014. Bivalve aquaculture transfers in Atlantic Europe. Part B: Environmental impacts of transfer activities. Ocean & Coastal Management, 89 p139-146
- Mortensen, S., 2000. Scallop introductions and transfers, from an animal health point of view. Aquaculture International, 8(2), p123-138
- Tang, B. et al, 2010. Physiological and immune responses of zhikong scallop Chlamys farreri to the acute viral necrobiotic virus infection. Fish & shellfish immunology, 29(1) p42-48
- Fish Health Inspectorate
- Fish Vet Group