Northern snakeheads in the tidal Potomac River system

A population of northern snakeheads Channa argus was documented within a 23-km reach of the main-stem tidal freshwater Potomac River and associated tributaries in 2004. Twenty northern snakeheads were collected with a variety of gears, including hook and line and electrofishing. The dominant habitats were shallow waters with floating or emergent vegetation. Natural reproduction had probably occurred, based on identification of five year-classes and the collection of an age-0 fish. The length frequency and age distributions suggested an established population. Many of the fish collected were gravid females. Adult total length (TL) and weight (W) ranges were 305-634 min (mean = 423 mm; SD = 76 mm) and 348-2,635 g (mean = 831 g; SD = 532 g). The length-weight relationship was log(e)W = -4.85 + 2.93(.)log(e)TL (r(2) = 0.99; n = 20). The collection pattern suggested that the northern snakeheads in the Potomac River originated from Dogue Creek, as 50% of those collected came from this watershed.