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Impact of the parasitic pea crab Pinnotheres novaezelandiae on aquacultured New Zealand green-lipped mussels, Perna canaliculus

Trottier, Oliver, Walker, Dion, Jeffs, Andrew G.
Aquaculture 2012 v.344-349 pp. 23-28
Perna canaliculus, biosecurity, control methods, crab culture, crabs, farms, industry, meat, mollusc culture, mussels, parasites, peas, New Zealand
Pea crabs are a common parasite of bivalves around the world and frequently cause problems for bivalve aquaculture through end-consumer complaints and rejections of consignments at international borders due to biosecurity concerns. However, the financial impact of pea crabs on aquaculture production has never been quantified for any bivalve species. A large scale systematic sampling of a typical green-lipped mussel farm in New Zealand revealed that pea crabs were present in 5.3% (±0.062 SE) of the mussels. The abundance of crabs increased gradually with decreasing water depth beneath the farm and greater distance from the shoreline. Mussels infected with pea crabs were 30% smaller in total wet weight [F₁, ₂₅₇₃=669, p=0.00], had a 29% lower meat yield [F₁, ₂₅₇₃=355, p=0.00], and shell dimensions were also significantly affected. A total production loss on the 1.71ha farm was estimated at 803kg at harvest. When this measured loss is extrapolated to current total mussel aquaculture production in New Zealand, pea crab infection represents an estimated loss to the industry of US$2.16 million annually. Our results indicate that parasitic pea crabs are producing a significant loss of production in shellfish farming aquaculture operations, even at low levels of infection, and therefore warrant a great deal more attention in terms of developing effective control measures.