Expansion of Northern Snakehead in the Chesapeake Bay Watershed

Abstract

Northern Snakehead Channa argus, a nonnative species to North America, was discovered in 2004 in tidal freshwater of the Potomac River, the second largest drainage of the Chesapeake Bay watershed. Since then Northern Snakehead has expanded its range throughout much of Maryland's portion of the Chesapeake Bay watershed. We estimated that the species has spread beyond its introduced range at a rate of about 2.7 subwatersheds per year. If that rate is maintained, the species will have spread its range throughout the entire watershed in 52 years. This rate has been consistent over time except for short periods of heightened expansion that followed an introduction of snakeheads into Delaware waters and in years with greater levels of spring precipitation. The expansion by Northern Snakehead is more widespread than that of other invasive fishes of Maryland's portion of the Chesapeake Bay, which include Blue Catfish Ictalurus furcatus and Flathead Catfish Pylodictus olivaris. Attempts to control the spread of the species have included public education, incentives for harvest, agency surveys, and law enforcement. The rapid natural and human‐aided expansion of Northern Snakehead throughout the country's largest estuary highlights the importance of laws that prevent live possession and importation of this species.

Emersion and Terrestrial Locomotion of the Northern Snakehead (Channa argus) on Multiple Substrates

“…Crowding may limit resources over longer periods of time and cause waste to accumulate, which could encourage emersion, but long-term studies on the effects of crowding on emersion are needed. The range expansion of northern snakeheads in the Chesapeake Bay Watershed appears to be correlated with rainfall and flooding ( Love and Newhard 2018 ), yet our precipitation treatment did not elicit emersion. However, we isolated the effects of precipitation to only include surface perturbations by falling water for a relatively short period of time.…”

“…As a freshwater fish, northern snakeheads would have difficulty osmoregulating in saltwater ( Evans 2008 ). They may be more likely to emerge in tidal regions, such as in the tidewaters of the lower Potomac River system where they are invasive ( Orrell and Weigt 2005 ; Odenkirk and Owens 2007 ; Love and Newhard 2012 ; 2018 ), or in coastal regions prone to flooding that may have rapid influxes of saltwater. However, their emersion demonstrates an intolerance of saltwater, making their expansion via coastal lagoons or embayments unlikely.…”

“…Combined, these traits suggest that northern snakeheads are capable of overland movements between bodies of water, especially when exposed to poor aquatic conditions or during flooding events when fish can be stranded on land or in small ephemeral bodies of water. As an invasive amphibious fish that is currently expanding its range in the United States, it is important to consider their amphibious behaviors and potential to colonize new bodies of water overland when regulating live possession and developing range expansion models and management plans ( Orrell and Weigt 2005 ; Odenkirk and Owens 2007 ; Love and Newhard 2012 , 2018 ).…”

“…The prevalence of snakehead fishes in the hobby aquarium industry and their value for food in Asian markets have led to their invasion throughout the United States and Europe ( Courtenay and Williams 2004 ; Orrell and Weigt 2005 ; Odenkirk and Owens 2007 ; Love and Newhard 2012 , 2018 ). Currently, several different species have established spawning populations in the United States, including the northern snakehead ( Channa argus ), which are particularly prevalent in the Chesapeake Bay Watershed.…”

Using Published Information to Predict Consumption by Northern Snakehead in Maryland

“…The species has increased in relative abundance by 10-fold to 100-fold since introduction into tributary streams of the Potomac River, the second largest river of the Chesapeake Bay watershed (the largest coastal estuary in North America). Since its introduction, the species has either maintained or slightly decreased in relative abundance in those streams (Odenkirk and Isel 2016) but has spread rapidly throughout the Chesapeake Bay watershed (Love and Newhard 2018). Northern Snakehead abundance has increased despite numerous initiatives to lower population sizes by encouraging harvest (Love and Genovese 2019).…”