A study on the prevalence of anisakid species in fish caught in Maltese waters

Abstract

From February 2015 to October 2015, 3 fish species were examined for the presence of anisakids. The larval abundance in these species was investigated, comparing the larvae count to the size and weight of the fish and the season in which they were caught. The study also compared results to a study performed in the previous year on fish caught from the same area, geographical subarea 15 (Maltese waters). Throughout the year 58 Chub Mackerel (Scomber Japonicus) were examined, 50 of which were found to be infected with anisakids with a total larval count of 832 larvae. The prevalence in winter was 100% with an average of 22.57 larvae per fish, spring was 72.7% with an average of 5.11 larvae per fish, summer prevalence was 100% with an average of 29.5 larvae per fish and autumn with a 75% prevalence and an average of 5.85 larvae per fish. The highest abundance was found to be summer followed winter, spring and autumn. Mackerel lengths varied from 27cm to 36 cm and the weight from 184 g to 310 g. No correlation was found between fish length, weight and parasite abundance. Out of the 55 infected mackerel, 23 samples underwent genetic analysis. Out of the 23 samples tested, 22 were PCR positive for either A.pegreffi and/or A.simplex s.s. 18 of the samples were found to infected with A.pegreffi, one mackerel had a mixed infection with both A.pegreffi and A.simplex s.s and three fish were infected with Acanthocephala thorny-headed worm.