The Occurrence of the Blood Fluke, Aporocotyle spinosicanalis Williams, 1958 in European Hake, Merluccius merluccius (L.) caught off the British Isles

Abstract

Of the 1,090 hake, Merluccius merluccius (L.), examined for Aporocotyh spinosicanalis, 323 were infected. Only adult flukes were found and these in the heart and bulbus arteriosus only; this habitat specificity and the apparent strict specificity of the fluke to hake are briefly discussed. The occurrence of from 1 to 5 flukes in each infected fish was common but up to as many as 60 were recorded. The incidence of infection is high in hake from shallow water in some areas to the west of Scotland; a particularly high incidence was found in the Minches and Sea of the Hebrides area. The incidence of infection was very low to the southwest of the British Isles and off Hartlepool in the North Sea; only 1 of 82 fish from these regions was infected. The possible use of A. spinosicanalis as a biological tag is discussed. A significant difference was found in the incidence of infection in hake of different length groups, the most heavily infected being those measuring 26 to 55.9cm.; small hake (25.9 cm. and below in length) from shallow water showed a low incidence of infection. Speculations are made on the possible course of the life-cycle of A. spinosicanalis. There was no significant difference in the distribution of the fluke in male and female fish and no obvious effect on the condition of the host was observed.