Nevada’s Smallest Fish and its Unique Habitat: Devils Hole Pupfish (Cyprinodon diabolis) and Devils Hole
Brandon Senger Supervising Fisheries Biologist – Southern Region 702-668-3999 [email protected] Agency Collaboration
National Park Service US Fish and Wildlife Service • Devils Hole is part of Death • Devils Hole Pupfish listed as Valley National Park Endangered under the • Endangered species occurring Endangered Species Act on lands administered through • Ash Meadows Fish Conservation the NPS Facility Devils Hole Pupfish
• Possibly most restricted habitat of a vertebrate species • Lives on the edge of physiological limits • Small, shallow body; lacks pelvic fins; reduced activity and aggression • 1-inch long • Sexually dimorphic • Lays a single egg each spawning event • Annual species • Endangered • Algae and macroinvertebrates Devils Hole, Nevada Spawning Shelf • 3.5 m wide • 5 m long • 0.3 m deep
Devils Hole Environment
• Limestone cavern, exposed aquifer • Crystal clear water • Very warm and stable temperature • 33.5 - 34°C (93°F) • Low Dissolved Oxygen • 2.5 – 3.0 mg/L • pH: ~7.4 • Energy limited • Very few nutrient inputs • Tidal fluctuations • Impacts from flash floods can be significant • Earthquake induced seiches • Unknown depth • Beyond 400 ft • Believed to be the deepest underwater cave system in the USA About that shaded area…
Solar Energy
• Algae • Inverts • Cover
(Wilson and Blinn 2007) Seasonal Resources
Winter Summer Additional terrestrial carbon • Terrestrial carbon • Algae Flood Events – Good? Bad? Depends???
• The Good • The Bad • Can provide nutrient input • Flood events can be very large • Cleans sediment off shelf and brings in new substrate • Crush eggs and larvae • Fish generally respond to • Clears off beneficial algae disturbance events • Observable increased activity, • Brings in new substrate… including spawning activity Too much of a good thing isn’t always good
• Implement management actions • What about pre-management times??? How does the Devils Hole ecosystem balance itself out after large flood events? September 7, 2017 September 8, 2017 Seismic events • Earthquake induced “seiches” • Oscillation in the water level creating an effect similar to waves • Earthquakes from thousands of miles away can induce seiches
• 8.1 Earthquake • Pijijiapan, Mexico
July 2019 Seiche July 4 – 6.4 Ridgecrest, CA July 5 – 7.1 Ridgecrest, CA
Before After July 4 earthquake After July 5 earthquake Management History
1930 1940 1950 1960 1970 1980 1990 2000 2010
• 1930 - Ichthyologist Joseph Wales completes first taxonomic description of Devils Hole pupfish
• 1952 – Devils Hole incorporated into then Death Valley National Monument by executive order • “…the said pool (Devils Hole) is of such outstanding scientific importance that it should be given special protection...evidenced by the presence in the pool of a peculiar race of desert fish…” - Proclamation of President Truman, January 17, 1952 Management History
1930 1940 1950 1960 1970 1980 1990 2000 2010 • 1967 – one of the first species listed as Endangered under the Endangered Species Preservation Act of 1966 • Listing in response to declining water levels from regional groundwater pumping
• 1976 – Supreme Court concludes minimum water level must be maintained Declining Water Levels
1950 1973 1970s Present day Fish Survey Methods
Early Life Stage Surveys Population Counts Population Counts Counts began in 1972
Surface Scuba SCUBA
• 1972 • Spring and Fall • 4 levels, count all fish on each level • ~50 minutes • 110 ft • Two scientific divers per dive • Overhead environment • Advanced scuba training • One safety diver assigned to each scientific diver Pupfish Abundance and Water Level
• 1960s -0.2 600 • Groundwater pumping significantly
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abundance a e M -1.2 Pupfish Population • Relatively stable population late Water Level 70s – early 90s -1.4 0
3 7 1 5 9 3 7 1 5 9 3 7 /6 /6 /7 /7 /7 /8 /8 /9 /9 /9 /0 /0 /1 /1 /1 /1 /1 /1 /1 /1 /1 /1 /1 /1 1 1 1 1 1 1 1 1 1 1 1 1 Date Population Decline
• Reason for decline remains elusive – Devils Hole a unique environment, no other comparative studies Devils Hole Pupfish Population • Hypotheses • Disease/introduced pathogen? 600 • Inbreeding/reduced genetic diversity = decreased fitness? Fall (September or October) • Change in ecosystem? 500 • Historically funding was limited
400 1967-1968 1999-2001
Spirogyra sp. Filamentous Cyanobacteria 300
200
100 Spring (March or April)
Ostracod sp. Neoclypeodytes cinctellus 0
Year Shift in Management Approach
Limited funding and general focus on Devils Hole Pupfish Population fish 600 Fall (September or October) • 2006 – NPS base funding 500
increase 400 • Development of ecosystem 300 monitoring program • Ecosystem monitoring nearly 200
absent during years of high 100 Spring (March or April) population counts • Reminder of how important 0 monitoring is during “good years” Year Recent Status and Actions
• 2006 and 2007 – 38 pupfish Devils Hole Pupfish Population • 2013 – 35 pupfish 600 • Low counts brought fear of extinction Fall (September or October) 500 • Low counts, resource limited, skinny fish = initiated supplemental feeding in winter 2006 400 300
200
100 Spring (March or April)
0
Year Ash Meadows Fish Conservation Facility
• Goal = secure, backup population of Devils Hole pupfish • Egg Recovery Mats • 10% of annual egg production • Eggs transferred to facility Ash Meadows Fish Conservation Facility • Aquaria for early life stage rearing • 110,000-gallon refuge tank • Replicate of Devils Hole shallow shelf • 2° cooler, high DO • 50% egg viability • 80% survival • Reproduction and multiple generations Recent highs
• Fall 2018 = 187 pupfish Devils Hole Pupfish Population • 15-year high! 600 Fall (September or October) • Spring 2019 = 128 pupfish 500
• 16-year high! 400
• Fall 2019 = 170 pupfish 300 • July earthquake, population size structure 200
100 Spring (March or April)
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Year