The bluefish, Pomatomus saltatrix, is often a preferred host for infection by the isopod, gill ectoparasite Lironeca ovalis. Here we quantify the occurrence of infection by L. ovalis on young-of-the-year bluefish in the Hudson River estuary and evaluate whether there is a significant reduction in growth or foraging as a result of infection. Prevalence of L. ovalis on bluefish was high (25.4%) but small (175 mm) exhibited significantly lower prevalences than intermediate-sized fish. Parasite size increased with bluefish size, and a significant but small effect of parasitism on the bluefish mass-length relationship was found; parasitized fish weighed 3% less than nonparasitized fish at a given length. Infection did not have a significant effect on the mass of stomach contents at capture. Although there remain many questions regarding the host-parasite relationship between P. saltatrix and L. ovalis, the physiological cost associated with infection appears to be small and probably does not constitute a serious threat to individual bluefish survival.