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Charles Birkeland , University of Hawai'i and USGS

Studying the effects of an introduced predatory grouper, roi ( Cephalopholis argus ) on a native Hawaiian reef fish assemblage. Charles Birkeland , University of Hawai'i and USGS Eric Conklin, The Nature Conservancy of Hawai'i Alan Friedlander, University of Hawai'i and USGS

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Charles Birkeland , University of Hawai'i and USGS

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  1. Studying the effects of an introduced predatory grouper, roi (Cephalopholisargus) on a native Hawaiian reef fish assemblage Charles Birkeland, University of Hawai'i and USGS Eric Conklin, The Nature Conservancy of Hawai'i Alan Friedlander, University of Hawai'i and USGS JonathaGiddens, University of Hawai'i at Hilo Chad Wiggins, The Nature Conservancy of Hawai‘i

  2. Topics • Roi (C. argus) in Hawaii • Roi removal study design • Study objectives • Approach • Progress • Next steps

  3. Roi(Cephalopholisargus) in Hawaii • Estimated population • 7.8 km2 reef = 56,290 roi consume 8.3 mil. fish/year • Surpass biomass of all other reef fish predators • Increasing with prey populations (DAR) Dierking, 2007

  4. What do roi ACTUALLY do to Hawaii’s reefs??? • Managers: • Science is equivocal • Community members: • Roi are a big part of why there are so few native fish

  5. Experimental roi removal design

  6. Experimental roi removal goals Address the following questions: Can we reduce roi populations with removal efforts? How do nearby roi populations respond? Do we know how many roi are out there? Does reducing roi populations change the native reef assemblage? Can we work with the fishing community on this project in a collaborative spirit that builds relationships and trust?

  7. Objective) Begin to experimentally assess the actual affect that roi have on native reef communities Approach: Collect baseline data on the structure and composition of benthic and reef fish communities Continue monitoring quarterly (for multiple years)

  8. Average fish abundance by feeding guild at three study sites F=10.4, p<0.001

  9. Objective) Create an independent estimate of roi populations via a depletion experiment Approach: • Calculate the original population density of roi in the removal area • Track catch per unit effort (CPUE) of fishers

  10. Objective) Quantify immigration into cleared areas Approach: • Externally tag roi around removal site • “Recapture” tagged individuals • Inside removal area • Via visual surveys • Via tag returns from community members

  11. Pre-removal tagging:

  12. Objective) Evaluate the efficacy of roi removal as a management tool Approach: Quantify the level of effort (time and money) required to fish roi down to <10% of original population.

  13. Next steps: Spearfishing! • Local spearfishermen dispatch roi and record information to determine: • Catch per unit effort • Length/weight ratios • Geographic distribution • Re-colonization rates/dynamics • Caught roi are used for: • Ciguatera research • Age/growth studies • Organic fertilizer

  14. Objective) Build stronger ties between coral reef managers, researchers, and the fishing community through an open collaborative approach Approach: • Contract two fisherman to help with experimental removal • Present project broadly within the community before, during, and after implementation

  15. Mahalonuiloa We are truly grateful for the opportunity to do this work, and especially want to thank: HCRI, NOAA, DAR Kona,Russell Amimoto, Kydd Pollock and all of TNC, KostaStamulous, Paolo Usseglioand UH manoa, Jim Beets, Bill Mautz, Cam Muir and UH Hilo, TCBESohana, Kawika, Mike, Rob White and the Roi Rally, Mike Kawamoto and the Hilo Dive Club, Darrell Tanaka and the Roi Round-up gang, The Puakō Community Association, Liz and Michael Morris family and friends and all of the community volunteers and supporters of marine conservation in Hawai’i.

  16. Questions? Photo: Rob Shallenberger

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