Effects of Fishing on Select Populations of Northern Snakehead in the Potomac River
Joshua J. Newhard, John S. Odenkirk, and Luke Lyon
Abstract.—Northern Snakehead Channa argus, a species native to parts of Asia, became established in the Potomac River drainage prior to 2004. Removals by agencies appeared to do little to control abundance or limit spread into new waterways. As such, Northern Snakehead has become widespread throughout much of the Potomac River drainage in addition to many other river systems throughout the Chesapeake Bay watershed. As abundance increased within the Potomac watershed, new recreational and commercial fisheries were developed by encouragement of state and federal agencies to increase harvest. A mark–recapture program to examine growth and movement of Northern Snakehead began in 2009, as population density appeared to be increasing. In 2013, tagging methods changed to allow population size of Northern Snakehead to be estimated within selected tributaries (Little Hunting Creek (LHC) and Upper Anacostia River (UA)). From 2009–2017 we used mark–recapture angler returns and agency sampling data to view population size in context with changes in fishing mortality. The UA population linearly declined with increasing fishing mortality, while the LHC population changed very little in response to fishing mortality except for 2016 which had the lowest population estimate and highest fishing mortality. We are cautiously optimistic that exploitation may help control population growth, but recreational fishing alone is unlikely to cause significant declines in Northern Snakehead populations. Furthermore, well-established populations are likely to require high (>25%) exploitation rates to be effective.