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Little Bugs, Big Data, and Colorado River Adaptive Management

This study explores the various factors that are limiting the population of Humpback Chub in the Grand Canyon, including temperature, flow regulation, non-native predation, and availability of food. The findings suggest that the limited diversity and production of aquatic insects is a key factor impacting fish populations. The study proposes potential solutions to mitigate these limitations.

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Little Bugs, Big Data, and Colorado River Adaptive Management

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  1. Little Bugs, Big Data, and Colorado River Adaptive Management Ted Kennedy, Grand Canyon Monitoring and Research Center

  2. What is limiting Humpback Chub in Grand Canyon? -Temperature -Flows -Non-native predation -Food

  3. Food web studies (2006-2009) Key findings: Only two common aquatic insects -‘stock portfolio’ is not diversified Invertebrate production is low -portfolio does not pay large dividends Botton line: Grand Canyon fish populations limited by invertebrate prey base Stock portfolio From Cross and others, 2013 Ecological Monographs Dividends

  4. But is having only two types of insects unusual for a tailwater? • %EPT: Nationally accepted metric for assessing river health • DIRECT measure of the ability of a river to support aquatic life • EPT = Ephemeroptera (mayflies) Trichoptera (caddisflies) Plecoptera (stoneflies)

  5. Yes, having only two types of insects (and no EPT) is unusual Regulated Rivers (within 25km of dam) Grand Canyon tributaries Glen Canyon Dam tailwater Bright Angel San Juan Shinumo Kootenai Flathead Madison Havasu Green Grand Canyon tributary data courtesy of Brian Healy, NPS. Tailwater data courtesy of Scott Miller, USU-BLM

  6. Fundamental Changes to Physical Template of Colorado River • Flow regime • High and low flows constrained • Greater within day variation (load-following) • Sediment regime • Inputs reduced by ~90% • Temperature regime • Cooler summer, warmer winter No control over these stressors

  7. Highly altered flow regimes Natural flow (estimated) Regulated flow (measured) Discharge (ft3/s) Schmidt and Grams 2011.

  8. Back to the drawing board • Load-following: obvious variable to consider • Prior insect studies investigated load-following • But focus was on larval life stages

  9. Need new study approaches • Larval studies limit learning • 25 years of larval studies failed to find a load-following bottleneck • Maybe bottleneck occurs at other life stages? A bottleneck at any of these life stages will limit aquatic insect populations

  10. Life history bottleneck at egg stage Kennedy and others, 2016, BioScience

  11. Load-following waves propagate far downstream Discharge at 4pm, May 30 River Mile Glen Canyon Dam Lake Mead

  12. Need Big Data? Try Citizen Science Distance from Glen Canyon Dam (km) Kennedy and others, 2016, BioScience

  13. Stepping outside of Grand Canyon C EPT = = Hydropeaking index = Daily coefficient of variation of discharge over 5+ yrs

  14. A Path Forward • Load-following is a significant filter • Imposes bottleneck at critical life stage • But insects are prolific • Maybe they just need a foothold EPT even found in contaminated sites Mayfly egg laying on San Juan River

  15. Mitigating load-following?Give bugs the weekend off!! • Steady and low flows every weekend May-Aug • Periodically create ideal egg-laying conditions Eggs laid here will never be desiccated

  16. Conclusions • Load-following flows constrain insect production and diversity in Grand Canyon • Leads to food limitation of fish populations • But Win-Win solutions still possible • Small tweaks to flow management can make a big difference

  17. Acknowledgements Thank you Grand Canyon River Guides!! • Scott Jernigan (242) • GibneySiemion (183) • Bob Dye (173) • Walker McKay (164) • Grand Canyon Youth (161) • Kelsey Wogan (124) • Eric Baade (92) • Kelly McGrath (46) • Connie Tibbits (38) And 11 others Collaborators: USGS: Jeff Muehlbauer, Charles Yackulic, Kim Dibble OSU: David Lytle USU: Scott Miller ISU: Colden Baxter Field and lab assistance • Eric Kortenhoeven • Anya Metcalfe • Tom Quigley • Moriah Evans • Jesse Fleri (USU) • Matt Schroer (USU)

  18. Questions?

  19. Spatial periodicity in midge abundance Midges: 3X greater at nodes Relative egg survival Kennedy et al. 2016 BioScience

  20. Low insect diversity in Grand Canyon

  21. Synoptic food web studies (2006-2009) Midges and blackflies key prey From Cross et al. 2013 Ecological Monographs

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