1. 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

2. 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

3. Biology Can breathe atmospheric oxygen Aggressive nest guarders
Image by VDGIF

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

5. 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

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

7. Potomac Introduction/Expansion
2004
2006

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

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

10. 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: /hr = 1 NSH/400 hrs
Carried out by VDGIF & USFWS
CPUE:
Largemouth bass: 0.98/hr
Northern snakehead: /hr = 1 NSH/175 hrs

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

12. 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

13. 2010 Radio Tagging
12 mature snakeheads implanted with radio tags
20mm

14. 2010 Radio Tagging

17. 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

18. 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

19. Questions?

20. 2009 Creel Survey 264 interviews
83% of anglers interviewed targeted largemouth bass

21. 2009 Creel Survey Do you think northern snakehead will impact…
Opinions toward targeting snakeheads…

22. 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

23. 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

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