Myxosporean Kudoa thyrsites: A Cause of Soft Flesh in Farm-Reared Atlantic Salmon

Abstract Smoked fillets of Atlantic salmon Salmo salar that were reared in sea-pens at a fish farm in British Columbia were found with softened and discolored areas. Examination of the affected tissue revealed infection with a parasite, the myxosporean Kudoa thyrsites. The smoking process (at 50°C for about 10 h) allowed proteolytic enzymes produced by the parasite to lyse areas of the fillet, resulting in poor-quality flesh. Inspection and culling of heavily infected fillets should reduce the immediate possibility of an inferior product reaching the market. Further work is necessary to define the extent of affected farm sites and to develop other handling and processing techniques for infected Atlantic salmon.