Blood parasites from fish of the Gulf of Maine to Cape Hatteras, Northwest Atlantic Ocean, with notes on the distribution of fish hematozoa

Abstract

Examination of blood smears from 657 marine fish collected from the continental shelf off the east coast of the United States, Cape Hatteras to the Gulf of Maine, revealed hematozoa in 19 of 39 species. Among the infected fish species, hemogregarines were more prevalent (17%) than trypanosomes (5%), piroplasms (4%), or trypanoplasms (1%). Ten species were infected with the virus that causes piscine erythrocytic necrosis. Prevalence of hemogregarines was higher in pleuronectiform and gadiform fish than among perciform species. Sedentary benthic species, especially flatfishes, and some demersal fish, were infected more often than pelagic species. Comparison of this survey with previous studies in the Northwest Atlantic suggests that hematozoa are more prevalent among fish in areas north of Newfoundland and decrease towards the equator. Piroplasms are reported only from fish occurring in temperate Atlantic waters. Piscivorous species of leeches, which are suspected or proven vectors of hematozoa, are more prevalent in the arctoboreal than in the neotropical Atlantic Ocean, and might account for the higher prevalence of piscine hematozoa in the northern latitudes.