Proceedings of the First International Snakehead Symposium

<em>Abstract.</em>—Relative weight and size structure indices are useful tools for fish biologists to characterize fish condition and fish size structure. However, a standard-weight (<em>W_s</em>) and size structure indices do not currently exist for Northern Snakehead <em>Channa argus</em>. We complied length-weight data from 4 established populations of Northern Snakehead in North America across five states and four drainages. We used the regression-line-percentile (RLP) method to develop a standard-weight equation for Northern Snakehead. The RLP method uses the 75th percentile as a benchmark for standard weight. Based this approach, we propose a metric standard-weight equation as log₁₀(<em>W_s</em>) = –5.142 + 3.0418 * log₁₀ (TL) with a minimum length of 200 mm; <em>W_s </em>is weight in grams and TL is total length in millimeters. For calculating proportional size distribution (PSD) we proposed the following length categories: stock, 190mm (7.5 in); quality, 340 mm (13 in); preferred, 420 mm (16.5 in); memorable, 550 mm (22 in); and trophy, 700mm (27.5 in). The population level indices developed in this study will provide fish biologists another set of tools to describe invasive Northern Snakehead populations in North America.