The metazoan parasite‐fauna of fish from Hanningfield Reservoir, Essex in relation to features of the habitat and host populations

A survey of the metazoan parasite‐fauna of eight species of fish from Hanningfield Reservoir, Essex was carried out between January 1968 and March 1969. 56 Brown trout, 89 Rainbow trout, 181 Perch, 165 Ruffe, 31 Roach, 31 Ten‐spined Sticklebacks, four Eels and one Stone‐loach were examined. In addition, 125 Rainbow trout were examined from adjacent raceways. Thirty‐one species of parasites were found, five Monogenea, nine Cestoda, eight Digenea, one Acanthocephala, four Nematoda, one Annelida, one Mollusca and two Crustacea. The possible origins of the parasite fauna are discussed. The relative abundance of different groups of parasites is considered in relation to the physical and biotic features of the habitat. Parasite species with planktonic crustacean intermediate hosts and/or avian final hosts are particularly abundant. The introduction of trout has resulted in an oligotrophic element being added to an otherwise eutrophic parasite fauna. Possible changes in the parasite‐fauna which may have occurred since construction of the reservoir are described. The parasite‐fauna of Rainbow trout from the raceways was found to be a reduced version of that of fish from the reservoir.