Long-term investigation of the ‘soft flesh’ condition in Northeast Atlantic mackerel induced by the myxosporean parasite Kudoa thyrsites (Cnidaria, Myxozoa): Temporal trends and new molecular epidemiological observations

Northeast Atlantic (NEA) mackerel (Scomber scombrus, Scombridae) represents an economically important target for the Norwegian pelagic fishing industry. Despite commercial significance of NEA mackerel, little is known about infections with myxosporean parasite Kudoa thyrsites (Kudoidae). The may cause post-mortem myoliquefaction fish skeletal muscle and therefore reduce quality product. In this study, we examined ‘soft flesh’ occurrence in size groups ‘autumn mackerel’ caught between 2007 2020, investigated prevalence density K. (qPCR) how they related to flesh’. present study first long-term investigation thyrsites-induced mackerel. After appearing stable over a decade, increased three- six-fold 2019 2020. This increase, together findings that seems primarily affect commercially most valuable group (>400 g), have implications industry fishery management. Molecular analysis suggests substantially higher than occurrence. majority (87.4%, n = 76/87) infected did not develop only individuals high musculature (12.6%, 11/87) showed condition. Therefore, qPCR analyses should be used estimating fish. method also assess risk