Invasive Fish in the Cariboo Region Russell Bobrowski Fisheries Biologist, BC Gov Cariboo Region Dec 19, 2017
Cariboo - Fishery Combination of productive lake and river fisheries 700 lakes with known game fish values 100 lakes stocked annually Significant river fisheries (Chilko, Dean, Horsefly, Mitchell rivers)
Background - Fishery Economic assessment of BC freshwater sport fishery in 2009 (economist Gordon Gislason) Cariboo Highest participation rate in BC 46,000 active anglers 440,000 angler days $75.5 million in direct expenditures 80% of angler effort comes from outside the Cariboo
Invasive Fish Species Illegal introduction of invasive species is a significant threat to native biodiversity and economically valuable fisheries Recent introductions: Smallmouth bass in Beaver Valley Goldfish in Dragon Lake Pleco/Plecostumus in Milburn Lake Pacu in Williams Lake Fathead minnow in Milburn
Smallmouth Bass Impacts on native fish and wildlife Voracious predator Reproduce faster than native species Reduce abundance and alter habitat use of native fish Biological Risk Assessment for Smallmouth Bass in British Columbia Upper Fraser Watershed- High probability of widespread invasion and high to very high ecological consequences
Smallmouth bass
Chinook Coho Pink Rainbow Suckers, Shiners, Peamouth Pikeminnows Rainbow Burbot Kokanee Whitefish Lake Trout BEAVER CREEK / BIG LAKE WATERSHEDS
2003 Bass illegally introduced in 2003 into Beaver Lake
2007 By 2007, bass had moved down to the Beaver Ck / Quesnel R confluence (first capture in July) and u/s from Beaver Lk
Future As the bass population builds in Beaver Ck, more bass will move throughout central BC
Actions to Manage Beaver Creek Bass Short term: control/contain - control numbers to minimize natural migration 2006-2009 - contain in smallest area possible through construction of barriers 2009-2011 - regulatory disincentives for anglers System closed for bass fishing Prevention: Public awareness program
Bass - Population Control In 2007, 2008 and 2009 we removed as many SMB from Beaver Ck watershed as possible
Bass - Containment Contain upstream movement Three year project: 2009-2011
Eradication- Chemical Treatment Rotenone: Organic Pesticide From the root of a plant in the bean family Used by Natives in South America Gardening Livestock tick removal
-affects gill breathing animals and invertebrates Eradication- Chemical Treatment
Eradication of Smallmouth Bass
7 year, $10 million project in 2012 (these costs were determined prior to discovery of bass in Big Lake) Cost of not eradicating the bass will be higher, over time Eradication plan developed (2012) Eradication resources have not been secured Efforts are ongoing Eradication Considerations Treatment is technically possible Large complex system, uncertainty of successful eradication Treatment will have to occur over 3-4 years
Bass in the Cariboo Region: What Next?
Dragon Lake - History First stocked with RB in 1927, then 1952 Not a successful trout fishery rehabilitation Treated in 1961 to remove non-game fish Toxaphene Restocked in 1963
Dragon Lake - History Re-opened in April 1964 Stocked with RB and EB (briefly)
Dragon Lake Present Day Continues to support high use fishery Significant recreational and economic benefits Primary producer of BW rainbow trout for provincial stocking program
Dragon Lake - Goldfish First confirmed in 2009 Small bodied, popular aquarium fish Not Koi (which reach significantly larger sizes)
Dragon Lake - Goldfish Very little information regarding goldfish in the wild Can mature after 1 to 2 years Well suited for warm summer water temperatures Increasing in density impact is uncertain
Dragon Lake - Assessment Angler effort - aerial boat counts - creel surveys Fish population - gill net surveys - FFSBC monitoring - creel surveys (catch statistics)
Angler Days Dragon Lake Summer Effort 16000 14000 12000 10000 8000 6000 4000 2000 0 1990 1994 1996 2002 2006 2007 2008 Year *flight line resumed in 2016
# fish / hr Winter Creels Catch Success Winter creels conducted in 1982, 1994, 2015 No significant change in catch success 0.2 0.16 0.12 0.08 0.04 0 1982 1994 2015
Fork Length (cm) Winter Creel Average Size No significant change in average size of fish captured 60 Some inter-annual variability 50 40 30 20 10 0 1982 1994 2015
Assessment Summary High use fishery summer effort to be evaluated 2016-2019 2012 stock assessment indicates healthy trout population (age structure, growth, etc) 2015 winter creel - Fish size and catch rates consistent with historical data FFSBC annual egg takes Healthy trout population
Management Options/Considerations Physical control/removal (netting; angling) - Continuous - Marginal effectiveness Chemical eradication - Effective removal - Socially sensitive
Current Management Plan - Population control volunteer removals Monitor fish community - Rainbow trout and goldfish - Standardized assessments and FFSBC Monitor fishery - Aerial boat counts 2016-2019 Public education and awareness
Prevention