DISTRIBUTION AND SEASONAL PREVALENCE OF HEMATODINIUM SP. INFECTION OFTHE NORWAY LOBSTER (NEPHROPS-NORVEGICUS) AROUND THE WEST-COAST OF SCOTLAND

Around Scotland, coastal stocks of the commercially important Norway l obster (Nephrops norvegicus), particularly those within the Clyde Sea Area (CSA), have for some years been known to be infected by syndiniid dinoflagellate endoparasites of the genus Hematodinium. The prevalenc es of infected Norway lobsters in trawl samples from-the CSA are repor ted for 1992-1995, together with similar data from a range of Scottish west coast sites in 1992, and from the Irish Sea in 1994 and 1995. In the CSA, infection prevalences declined after 1992 and were higher th an those recorded in other sampled areas. Infection by Hematodinium wa s cofined to the first half of the year, peaking in the spring and ear ly summer, with medium-sized and female lobsters showng the highest pr evalence. Comparison between CSA sites suggests that infection may be influenced by factors directly related to Nephrops age rather than siz e. In addition to the usual diel variability in catch, in spring male Nephrops showed diel variability in Hematodinium prevalence in trawl s amples (being higher in the midnight samples). Females showed no diel variation in prevalence. Underwater television surveys of Nephrops bur row density and data on commercial landings indicate a decrease in Nep hrops abundance in the last decade, which might in part reflect the hi gher levels of infection by Hematodinium during this time. (C) 1998 In ternational Council for the Exploration of the Sea.