Abstract

The Northern snakehead fish (Channa argus) is a nonnative species that has over the past decade become well established within the Potomac River system of the mid-Atlantic region. Northern snakehead are large piscivorous predators that are highly adaptable within temperate freshwater habitats. Since they were initially observed in the region in 2002, their population has apparently expanded considerably within the Potomac River system. Over the past several years, many aspects of Northern snakehead life history in the Potomac River have been described, including microhabitat selection, range and dispersal patterns, spawning behavior, and diet. However, comparatively little is known about their health status including susceptibility to parasitism and disease and their capacity to serve as reservoirs of disease for native wildlife. Although considered immunologically hardy, this species has demonstrated susceptibility to a number of described piscine diseases within their native range and habitat in Asia. Significant reported diseases of snakehead in Asia include snakehead rhabdovirus, epizootic ulcerative syndrome, nocardiosis, and mycobacteriosis.

Health screening of Northern snakehead from the Potomac River system conducted over the past several years by our laboratory has detected few disease-related issues. Reported problems include incidental findings of parasitism of gill, skin and musculature with protozoa, monogenes, and trematodes, and infection with Ichthyophthirius multifiliis in one laboratory-maintained, wild-caught group. Screening of Potomac River snakehead populations also has shown these fish to asymptomatically harbor a viral agent producing cytopathic effect in cell culture. The agent was subsequently identified as largemouth bass virus based on PCR amplification and partial sequencing of the major capsid protein. Investigations are currently underway to determine the ability of this viral isolate to produce disease within Northern snakehead and other potentially susceptible native fish species. Recent observation of an acid-fast organism associated with granulomatous inflammation in wild-caught Northern snakehead specimens from the Potomac River system is also currently under investigation. Continued research concerning the pathogens and diseases of this introduced species is important to fully understanding its potential impacts on this aquatic ecosystem.

* Presenting author