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Invasive poeciliids alter ecological structure, function and biodiversity in Hawai`i

Invasive poeciliids alter ecological structure, function and biodiversity in Hawai`i. T. Holitzki 1 , R. MacKenzie 2 , K. McDermid 3 and Tracy Wiegner 3 TCBES UHH 1 , USDA Forest Service IPIF 2 , UHH Marine Science 3. 50 – 90% of nekton community dominated by invasive fish.

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Invasive poeciliids alter ecological structure, function and biodiversity in Hawai`i

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  1. Invasive poeciliids alter ecological structure, function and biodiversity in Hawai`i T. Holitzki 1, R. MacKenzie 2, K. McDermid 3 and Tracy Wiegner 3 TCBES UHH 1 , USDA Forest Service IPIF 2, UHH Marine Science 3

  2. 50 – 90% of nekton community dominated by invasive fish MacKenzie and Bruland in review

  3. Research objectives To document how poeciliids are affecting Hawaiian streams. H1. Poeciliids increase nutrient yields through excretion H2. Poeciliids increase algae through increased nutrients H3. Poeciliids decrease invertebrates through consumption H4. Poeciliids decrease native fish densities through resource competition H5. Poeciliids are altering the food web structure of Pacific Island streams

  4. Study site • Substrate • Riparian canopy • Watershed • Land use • Elevation • Stream width

  5. Methods • Physicochemical parameters • Nutrient sampling • Algae collection • Macroinvertebrate collection • Fish measurements

  6. Poeciliids increased NO3- and TN yields

  7. Fish excretion flux rates higher in invaded streams

  8. Chlorophyll a and ash-free dry mass higher in poeciliid streams

  9. Total invertebrate densities lower in poeciliid streams

  10. Macroinvertebrate percent contribution

  11. Fish densities 0 0 0

  12. R.MacKenzie

  13. Conclusion • Poeciliids increased: • NO3-, and TN yields • Benthic chl a and AFDM • most macroinvertebrate groups • Poeciliids decreased: 1. chironomids 2. Hydroptila spp. 3. native fish densities Lentipes concolor

  14. Acknowledgments • Advisors : Richard MacKenzie, USDA Forest Service, IPIF Karla McDermid, UHH Marine Science Tracy Wiegner, UHH Marine Science • All my sampling partners (Caitlin Kryss, Lori Tango, Lindsey Shimizu, Mike Foster, Topaz Collins, Cassie Lyons and Bond Segal) • USDA Forest Service, UHH Analytical Lab (Lucas Mead) • Kevin Hopkins, Matt Barton • REAP grant and PRISM award

  15. Questions?

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