Managing Amphibians in the Wildcat Creek Watershed
Managing Amphibians in the Wildcat Creek Watershed Ed Culver – Fisheries Resource Analyst Joe Sullivan – Fisheries Program Manager Tammy Lim – Wildlife Resource Analyst Jakob Woodall – Fisheries Intern
2004- 2010
20 18 16 14 12 10 8 6 4 2 0 2011
20 18 16 14 12 10 8 6 4 2 0 2012
20 18 16 14 12 10 8 6 4 2 0 2013
20 18 16 14 12 10 8 6 4 2 0 2014
20 18 16 14 12 10 8 6 4 2 0 2015
20 18 16 14 12 10 8 6 4 2 0 2016
100 90 Scale Change! 80 70 60 50 40 30 20 10 0 2017
100 90 80 70 60 50 40 30 20 10 0
Historic CRLF 2013 Observations
2011
2001 Newt Treefrog Western Pond Turtle Coast Garter Snake Red- eared Slider Bullfrogs - April Bullfrogs - May Bullfrogs - June Bullfrogs - July Bullfrogs – August Fyke Netting in Lake Anza Fyke Netting in Jewel Lake Lake Anza Jewel Lake
American Bullfrog – 8 sub-adult Catch American Bullfrog - tadpole 624 470 Results Largemouth Bass 112 Green Sunfish 39
Golden Shiner 16
Rainbow Trout 1
Mosquitofish 1 316
Three-spined 543 Stickleback
California Newt 10
Sierran treefrog 3
Red-eared Slider 1
Western Pond Turtle 3
Red Swamp Crayfish 23 18 Botanic Garden Pond Draining
Photo by L. Bittner Photo by A. Narayan Results of Botanic Garden Pond Draining • Removed 44 Bullfrogs • Collected 266 newts (safely moved to nearby settling pond) • THOUSANDS of newt sub-adults • Pond drained to ¼ capacity • Many of the Bullfrogs collected were gorging on newts Stomach Contents Stomach Contents
Newt 24 Snail 26 Insect 34 Treefrog 1 Rodent 1 Empty 9 Wood Debris 3 2017
100 90 80 70 60 50 40 30 20 10 0 2018
800 700 Scale Change! 600 500 400 300 200 100 0 Bullfrogs 2004-2018 1400
1200
1000
800
600 Individuals Collected Individuals 400
200
0 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Management • What we learned: • We relied on visual observations, hand capture of individuals, and salvage during fisheries surveys • Catch rate is inefficient compared to more active sampling methods • Fyke nets provided lots of by-catch of tadpoles, but are not an efficient method of sampling for bullfrogs adults • Pond draining proved efficient at removal of bullfrog sub-adults inhabiting a small pond (30 ft x 40 ft x 3ft) • Required equipment and staff time • Better understand where bullfrogs are • How do they move in landscapes? What habitats do they use? • Ponds near bullfrog source populations have high probability of ‘invasion’ • We need more ‘eyes on the ground’ – we don’t yet have a clear picture of where bullfrogs have established themselves in EBRPD • Work with park staff to create a list of bullfrog invasion sites • Better understand bullfrog co-occurence with native species • More surveys and management of areas where bullfrogs are present in critical habitat of CRLF and CTS Documented by Mason Holmes of Santa Clara Valley Water District Management • Recommendation for a specific management plan • How do we prioritize which ponds to manage? Co-occurrence with CTS and CRLF? Proximity to already invaded ponds? Proximity to pond management in association with EBMUD? • What permitting do we need? What other tools can we use that we aren’t now? What can we learn from other agencies who have already embarked down this path? • Other agencies in the area have Bullfrog Management Plans that allow them to do more active management (air-rifles, active capture and netting, traps, and pond draining) Future Steps – Collaborations/Student
Research Projects Photo Credit: Bev Sykes • Predation of newts by bullfrogs • Mortality from Wildcat Canyon Rd - • Possible ‘Newt Tunnel’? • More complete survey of bullfrogs across the watershed, including winter dispersal surveys • Amphibian use and movements near restored EEC ponds • Bd(chytrid) in amphibians in Wildcat Creek Acknowledgements Joe Sullivan, Tammy Lim, Jakob Woodall, Sean O’Neil EBRPD GIS Department (Kara Boettcher and Christie McKaskey) EBRPD Botanic Garden Staff (Liz Bittner, Bart O’Brien, Michael Uhler, Don Fuller, Theo Fitanides, Audrey Maxwell, Chris McCarron) EBMUD (Jessica Purificato and Hannah Fertel)
Photo by J. Didonado