INFLUENCE OF THE TRANSMISSION OF PARASITES FROM PREY FISHES ON THE COMPOSITION OF THE PARASITE COMMUNITY OF A PREDATORY FISH

Helminth parasites and diet of seven freshwater fishes (Lota lota and six common prey species) from the Bothnian Bay, Baltic Sea, were studi ed monthly or bimonthly during 1978. Twenty-one of the 32 parasites wi th complex life cycles were shared between Lota lota and its prey fish es and are thus transmissible from prey to predator. Gymnocephalus cer nuus and L. lota had the greatest number of shared species (13). Larva l and adult cestodes, nematodes, and acanthocephalans could re-establi sh in the predator, but only one adult trematode was capable of this t ransition. Infracommunity species diversity was highest in L. lota (e( H') = 3.54), which also had the most species (24), the highest mean nu mber of species and individuals of a given species per fish (6.3 and 6 2, respectively), and the greatest number of worms in one fish (520). Variety of diet was key in determining exposure to parasite species. H owever, most specificity finally determined if a given parasite could establish and mature. No ecologically explicable suites of parasites w ere found in any fish species, except in a few cases where parasites u sed related intermediate hosts. However, the composition of these suit es was not retained in the predator. Unlike in L. lota, important para sites of prey fishes were typically specialists.