OCCURRENCE AND EFFECT OF THE PARASITIC ISOPOD, LIRONECA-OVALIS (ISOPODA, CYMOTHOIDAE), ON YOUNG-OF-THE-YEAR BLUEFISH, POMATOMUS-SALTATRIX (PISCES, POMATOMIDAE)

The bluefish, Pomatomus saltatrix, is often a preferred host for infec tion by the isopod, gill ectoparasite Lironeca ovalis. Here we quantif y the occurrence of infection by L. ovalis on young-of-the-year bluefi sh in the Hudson River estuary and evaluate whether there is a signifi cant reduction in growth or foraging as a result of infection. Prevale nce of L. ovalis on bluefish was high (25.4%) but small (<75 mm) and l arge fish (>175 mm) exhibited significantly lower prevalences than int ermediate-sized fish. Parasite size increased with bluefish size, and a significant but small effect of parasitism on the bluefish mass-leng th relationship was found; parasitized fish weighed 3% less than nonpa rasitized fish at a given length. Infection did not have a significant effect on the mass of stomach contents at capture. Although there rem ain many questions regarding the host-parasite relationship between P. saltatrix and L. ovalis, the physiological cost associated with infec tion appears to be small and probably does not constitute a serious th reat to individual bluefish survival.