Internal Parasites of Tropical Pelagic Elasmobranchs and Mesopelagic Teleosts

Grant Winners

Dean

Abstract

Natural mortality is a poorly known aspect of fisheries biology, despite its importance in stock assessments and population analysis. Of the many potential sources of mortality and morbidity in fishes, the effect of gastrointestinal parasites is perhaps the least studied. Parasite loads in the elasmobranch spiral valve and teleost fish gastrointestinal tract may both inhibit nutrient uptake and stimulate an inflammatory response in the host. The gastrointestinal parasites of several tropical pelagic elasmobranchs including dusky, silky, and night sharks (Carcharhinus obscurus, C. falciformis, and C. signatus), the pelagic stingray (Pteroplatytrygon violacea) and the mesopelagic fishes snake mackerel (Gempylus serpens), oilfish (Ruvettus pretiosus), and escolar (Lepidocybium flavobrunneum) will be described from the South Atlantic Bight in the western North Atlantic as well as the Gulf of Mexico. These species were chosen for availability factors as well as their lack of sufficient parasitic species load information in an attempt to expand the range of knowledge on the potential mortality factors of these species. Specimen collection of these species is being performed aboard a designated pelagic longline vessel with a certified observer on board. Laboratory techniques include setting, staining and mounting the parasites for identification. The collected parasites will be identified to the lowest taxonomic level and characterized as commensal or detrimental to the host with the aid of a key composed on site. Each parasite found within the sample hosts will be described and documented by identifiable morphological characters such as gonads, buccal cavity and scolex placement. Parasitic species found to date in preliminary work include nematodes, trematodes and cestodes. Total gastrointestinal parasite loads will be compared against the size (length and weight) and sex of the host.