Insight into Age and Growth of Northern Snakehead in the Potomac River

Abstract

A Northern Snakehead Channa argus population was documented in the Potomac River system in 2004. Since that time, the population has expanded in range and number, yet relatively little is known about key population variables including age and growth. Lack of known-age fish with which to compare otoliths from the sampled population has hindered verification, and Northern Snakehead otoliths can be difficult to interpret. We compared growth increments (mm/d) of recaptured fish marked with T-bar anchor tags (n = 51; mean time at large, 310 d [SD = 302]) to otolith annuli from fish sacrificed in 2011 and 2012 (n = 192). While immersed (solution of 80% water and 20% glycerin) otolith transverse perspectives were viewed “cracked” with transmitted light. Readings from fish aged 1–4 years suggested initial growth was much faster than previously reported, but length at age was highly variable. Annual growth increments for fish aged 1–4 (mean length at age of fish, respectively: 394, 563, 644, and 721 mm TL) were converted to estimated daily growth (mm/d), which was reasonably similar to the daily growth of recaptured tagged fish. Von Bertalanffy growth parameters were L_∞ = 780, K = 0.48, and t ₀ = −0.56, where L_∞ is the asymptotic length, K is a growth coefficient, and t ₀ is a time coefficient at which length would theoretically be zero. The implications of rapid growth include the potential for the earlier onset of sexual maturity, which could represent enhanced chances for successful colonization.

Received November 20, 2012; accepted May 15, 2013

ACKNOWLEDGMENTS

This study was funded, in part, through Federal Aid in Sportfish Restoration Grant F-111-R. We thank all the VDGIF biologists, Conservation Police Officers, technicians, and volunteers who assisted in field collections.