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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 Slide 2 50 90% of nekton community dominated by invasive fish MacKenzie and Bruland in review Slide 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 Slide 4 Study site 1.Substrate 2.Riparian canopy 3.Watershed 4.Land use 5.Elevation 6.Stream width Slide 5 Methods Physicochemical parameters Nutrient sampling Algae collection Macroinvertebrate collection Fish measurements Slide 6 Poeciliids increased NO 3 - and TN yields Slide 7 Fish excretion flux rates higher in invaded streams Slide 8 Chlorophyll a and ash-free dry mass higher in poeciliid streams Slide 9 Total invertebrate densities lower in poeciliid streams Slide 10 Macroinvertebrate percent contribution Slide 11 Fish densities 000 Slide 12 R.MacKenzie Slide 13 Conclusion Poeciliids increased: 1.NO 3 -, and TN yields 2.Benthic chl a and AFDM 3.most macroinvertebrate groups Poeciliids decreased: 1. chironomids 2. Hydroptila spp. 3. native fish densities Lentipes concolor Slide 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 Slide 15 Questions?