SEAFWA 2015

Matthew R. Womble, Raphael Orelis-Ribeiro, Jackson R. Roberts –, Southeastern Cooperative Fish Parasite & Disease Project, Auburn University; Jacob M. Rash, Doug A. Besler –North Carolina Wildlife Resources Commission; Cova R. Arias, Stephen A. Bullard* – Southeastern Cooperative Fish Parasite & Disease Project, Auburn University

Salmincola (Copepoda: Lernaeopodidae) comprises 17 species that infect the epithelial surfaces (gill, buccal cavity) of 11 genera of freshwater fishes assigned to Salmonidae, Esocidae, Cottidae, and Gadidae of North America, Europe, and Asia. Southeastern United States trout fisheries comprise rainbow trout Oncorhyncus mykiss, brook trout Salvelinus fontinalis, and brown trout Salmo trutta. Of which, two (rainbow trout and brook trout) are infected by species of Salmincola: S. californiensis infects gill of rainbow trout [primarily] and brook trout in 13 states; whereas, S. edwardsi infects gill of brook trout (primarily) and rainbow trout in 4 states. Salmincola spp. have direct life cycles (not requiring an intermediate host) and are associated with fish disease such that infections on wild and cultured fish are cause for legitimate concern, amplified biosecurity, and routine monitoring. For example, infections on farmed rainbow trout may cause appetite inhibition, liver discoloration, and gill lamellar hyperplasia associated with loss of respiratory function. In the present report, Salmincola infections were observed in the gill and buccal cavity of rainbow trout from a private trout farm on the Watauga River (81% prevalence; 6.6 mean intensity), from adjacent sites on that river (11% prevalence; 2.0 mean intensity), and from the West Fork Pigeon River as well as from gill and buccal cavity of brook trout from the upper Cullasaja River. Grossly, heavily-infected rainbow trout from the hatchery exhibited alterations to the normal gill filament architecture that indicated a reduction in functional respiratory surface. Histopathology and scanning electron microscopy revealed branchial epithelium hyperplasia, occluded interlamellar water channels, and inflammation indicative of a chronic lesion associated with attachment and/or feeding of mature female copepods. The marked lesion could be interpreted as a ‘mismatched’ host-parasite relationship, speculatively resulting from a recent introduction of the parasite, or that of the rainbow trout strain, into the Watauga River. To our knowledge, this is the first confirmed occurrence of Salmincola in rivers of North Carolina and the Southeastern United States, although anecdotal reports of previous Salmnicola infections among hatchery-reared fishes in the region exist.