Parasite causing problems for B.C. salmon farmers
Some B.C.-farmed salmon is reaching store shelves with a parasite that can liquefy the fish’s flesh into an unappetizing goop.
CTV British Columbia recently heard from a shopper who picked up a salmon fillet from a large retailer. After noticing the fillet had large holes throughout the flesh, he brought it back to the store for a refund.
It turned out the fish had been infected with Kudoa thyrsites, a parasite that is causing a big problem for fish farmers in B.C. and elsewhere.
Kudoa thyrsites is a parasite that is found in all wild and farmed fish, and has become the second most common parasite in farmed salmon in B.C.
While the parasite doesn’t hurt the fish, it can survive in its flesh long after the salmon is killed. It then causes a condition dubbed “soft flesh” syndrome, in which the fish fillets fall apart, or even turns into a jelly -- technically called “post-mortem myoliquefaction."
“This parasite is like this time bomb inside the fish,” John Volpe, a University of Victoria environmental studies professor, told CTV British Columbia.
The parasite isn’t thought to pose a health risk to humans but because there is no way to treat an infection at a fish farm, large quantities of the fish often have to be destroyed.
Marine Harvest Canada, B.C.’s largest supplier of B.C. farm-raised salmon, says Kudoa thyrsites was a significant problem for the industry in 2011.
The parasite was discovered in B.C. farmed salmon in the early 1990s and now affects a significant portion of all salmon farmed in the province.
Marine Harvest says it spent $12 million last year to discard infected fish and provide refunds for tainted products.
The group’s spokesman, Ian Roberts, says most infections are caught long before infected fish reaches the consumer.
“It’s rare that someone would find this in the market,” he told CTV British Columbia, adding that it’s “unacceptable” that the consumer who spoke to CTV was able to buy an infected fillet.
What’s frustrating for fish farmers is that little is known about Kudoa’s life cycle and how and when fish become infected. Diagnosing a problem in live fish is also still difficult.
Marine Harvest Canada and the B.C. Center for Aquatic Health Sciences have embarked on a three-year, joint research project to increase the understanding of Kudoa thyrsites.
With a report from CTV British Columbia’s Mi-Jung Lee