Distribution expansion of the invasive northern snakehead in the United States By: Josh Newhard Steve Minkkinen Ian Park U.S. Fish and Wildlife Service Maryland Fishery Resources Office

Biology of northern snakehead (Channa argus) Maximum Length- 1 meter Typically found in temperate waters Can tolerate cold water during winter Mature at 2 years Reproduce in late spring/early summer May spawn multiple times per year

Biology Can breathe atmospheric oxygen Aggressive nest guarders Image by VDGIF

History Native to Asia Methods of introduction: Common in aquarium trade Live-fish food market

Introduction to U.S. FL canals in 2000 Pond in Crofton, MD in 2002 Potomac River in 2004 Arkansas 2008 Pennsylvania 2008 New York 2008

Control Methods Rotenone Removal Non-specific piscicide Capture and kill Efficient?

Potomac Introduction/Expansion 2004 2006

Expansion in Potomac 2008 2010 N. Snakehead caught in Nanticoke Tributary

Current Potomac Research Goals to better understand snakehead movements and population size Creel Surveys Cooperative Tagging Program Radio Tagging

Creel Surveys 2008 Creel Survey 2009 Creel Survey Done by Virginia Dept. of Game and Inland Fisheries (VDGIF) CPUE: Largemouth Bass:1.03 /hr Northern snakehead: 0.0025/hr = 1 NSH/400 hrs Carried out by VDGIF & USFWS CPUE: Largemouth bass: 0.98/hr Northern snakehead: 0.0057/hr = 1 NSH/175 hrs

Cooperative Tagging Program Partnership with state agencies VA MD DC First tagging began in Spring 2009 Rely on agency & angler recaptures

Cooperative Tagging Program 881 Tagged, 85 Recaptures (~9.6%) Longest time at large- 387 days Fish had moved downstream 28 river km 90% of recaptures in same creek as initial capture Farthest “migration” was 46.3 river km upstream from initial capture

2010 Radio Tagging 12 mature snakeheads implanted with radio tags 20mm

2010 Radio Tagging

Summary/Future Directions Distribution within Potomac is expanding Expansion outside of Potomac? Continued analysis of mark-recapture data for population estimates Monitor radio tagged fish for one more year Working with MDDNR to monitor possible impacts on largemouth bass by northern snakehead

Recommendations for control Creel surveys every 2-3 years Excellent way to monitor recreational catch rates Targeted removal during peak capture times During spring, pre-spawn period and during winter Continued angler education Helps in preventing further spread to other waterways

Questions?

2009 Creel Survey 264 interviews 83% of anglers interviewed targeted largemouth bass

2009 Creel Survey Do you think northern snakehead will impact… Opinions toward targeting snakeheads…

Arkansas April 2008 Spawning populations of NSH in Piney Creek Confined in Piney Creek watershed Tributary to Big Creek, White River, Mississippi River Awaiting Commission approval and looking for funding to eradicate NSH in Piney Creek

Pennsylvania First discovered in ponds at FDR Park in South Philadelphia NSH found in tidal portion of Schuylkill River near Philadelphia Angler confirmed capture, 8.3 miles upstream of Delaware River Tributary to Delaware River

New York May 2008 Three NSH captured Catlin Creek, Ridgebury Lake Tributary to Hudson River Proposing to Rotenone