Bullseye Snakehead in Florida; FWCC s Approach to a Non-Native Fish Kelly Gestring Non-Native Fish and Aquatic Wildlife Coordinator
FWC s Non-Native Fish Program Established in 1970 to address FWC s concerns over exotic fishes: 1. Alter energy flow through fish communities 2. Introduction of parasites and diseases 3. Unpredictable 4. May compete with native fishes for food, shelter, or space
NNFP s historical approach to address non-native fish concerns: PREVENTION *ASSESSMENT* MANAGEMENT
Specific Objectives of NNFP 1. Document the distribution and abundance of exotic fishes in Florida. 2. Define their life history strategies, environmental limiting factors, population dynamics, and associations with native fishes. 3. Develop management plans that incorporate these species.
Bullseye Snakehead in Florida Popular sport and food fish in native range but illegal to possess alive in Florida since mid-1960s. Source of introduction =????? One of 23 established non-native fish.
Rapid Response Bullseye Snakehead 2000 Oct 5 (4pm): First reported from Tamarac area by an angler. Oct 6: Confirmed in multiple, interconnected home owner and golf course ponds making eradication nearly impossible. Oct 10: Confirmed presence and likely establishment in Cypress Creek Canal thereby making eradication impossible and ASSESSMENT mandatory.
Bullseye Snakehead Laboratory Identified Temperatures Stopped Feeding = 14-16 o C Death = 10-12 o C (n = 6; R = 193-372 mm TL) Potential range south of Gainesville
Known Range of Bulllseye Snakehead as of 10/31/2013 Shaded area represents approx. 5% of their LLT-based potential range
Reproduction Mean Fecundity Estimate = 5,280 per ripe female Spawn primarily between March and June
Largest snakehead (14.25 lbs, 37.7 in female collected to date. Pending IGFA All Tackle record of 14.0 lbs
Top BS Prey Items Mosquitofish, swamp darter, crayfish, and Bufo (toad + tadpoles) collectively: 1. Occurred in 47% of bullseye snakehead stomachs examined, and 2. Made up >19% by number and >28% by volume of the total prey items identified in nearly 1,800 fish (microcrustaceans comprised 51% by number but <1% by volume)
Mosquitofish: One of principal prey species for bullseye snakehead
Crayfish: One of principal prey species for bullseye snakehead
Predaceous Diving Beetle, insects important prey in small fish
Bufo (Toad + Tadpoles): On principal prey species in bullseye snakehead
Cannibalistic Snakehead Found in 12 fish, and comprised <1% by number and 5% by volume
Water snake
Fish Community Analyses of South Florida Urban Canals NNFL developed method of using detonating cord to collect quantitative fish community samples
kg/ha Cypress Creek Canal (C-14) Fish Community Estimates (two 0.185 ha blocknet samples per year) 400 375 Total Exotic Fishes Total Native Fishes 350 Grass Carp Sportfishes 325 Mayan Cichlid Bream 300 Bullseye Snakehead Largemouth Bass 275 250 225 200 175 150 125 Total Native Fish Mean 100 75 50 25 0 1988 1999 2001 2002 2004 2006 2007 2008 2009 2011 No significant negative correlations found Similar results in Hillsboro Canal
STANDARDIZED ELECTROFISHING
CPM 24 20 16 Cypress Creek Canal (C-14)-Standardized Daytime Electrofishing (3-15 min transects) Total Exotic Fishes Grass Carp Mayan Cichlid Bullseye Snakehead Total Native Fishes Sportfishes Bream Largemouth Bass 12 8 4 0 1997 1998 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 No significant negative correlations found Similar results in Hillsboro Canal
Angling Attributes- Wise-use or cause for concern? Based on LLT of 10 0 C, Only occupy approx. 5% of potential range. Anglers may spread them
Snakeheads caught using similar tackle as largemouth bass
The average Hg level for 131 bullseye snakehead (13.7-34.3 in) from 9 sites was 0.14 ppm, well below the DOH s 0.50 ppm caution level = Safe To Eat! Catch em, Keep em, and Eat em! Snakehead look and act like bowfin, but at suppertime there s no comparison
SNAKEHEAD ROUNDUP Catch, Keep, and Kill tournaments Sponsored by local bait manufacturing company Snakehead tournaments: harvesting some fish, providing some socioeconomic benefit
Bullseye Snakehead Conclusions were illegally introduced and have become established and abundant in several southeast Florida canal systems. grow to large size (ca 15 lbs), look & act like bowfin, are unwanted and undesirable though highly prized as human food. are cause for concern, but catastrophic descriptors are not warranted nor currently scientifically justified.
CONCLUSIONS and OTHER MUSINGS Although their presence is unwanted, past studies discredit many commonly held beliefs that established exotic fishes in Florida: cause native fish extinctions have direct negative effects on native fishes can be eradicated are always detrimental
QUESTIONS?