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Mason Segura, Jeff Wesner and Mark Belk Department of Biology Brigham Young University

Spatial variation in the trophic position of freshwater fishes in the Bear River Drainage, Great Basin, Utah. Mason Segura, Jeff Wesner and Mark Belk Department of Biology Brigham Young University. Background. Northern leatherside chub. Upper Bear River (UT, WY), Snake River

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Mason Segura, Jeff Wesner and Mark Belk Department of Biology Brigham Young University

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  1. Spatial variation in the trophic position of freshwater fishes in the Bear River Drainage, Great Basin, Utah Mason Segura, Jeff Wesner and Mark Belk Department of Biology Brigham Young University

  2. Background Northern leatherside chub Upper Bear River (UT, WY), Snake River Threatened species Described in 2004 Need ecological information for management and recovery

  3. Background Northern leatherside chub 2010/11 - Factors affecting abundance 2010/11 - Factors affecting occurrence

  4. Some sites have good habitat, but no leathersides Leath. absent Leath. present 2010/11 - Factors affecting abundance 2010/11 - Factors affecting occurrence Current - Factors affecting food webs (trophic position, food chain length)

  5. Does trophic level vary across sites? • Are trophic positions of common species different at sites with/without northern leatherside chub? Redside shiner Northern leatherside chub Similar habitat requirements Similar life-histories Similar foraging strategies Similar isotopic niches Positive co-occurrence and abundance REDSIDE IS COMMON, LEATHERSIDE IS RARE

  6. N Bear River

  7. Stable isotope analysis • 14 sites • 5 species • 10-15 individual fin clips per species • all adults • algae, aquatic insects, terrestrial insects, terrestrial plants • Analyzed stable isotopes of C14 and N15

  8. Stable isotope analysis • 14 sites (9 analyzed so far) • 5 species • 10-15 individual fin clips per species • all adults • algae, aquatic insects, terrestrial insects, terrestrial plants • Analyzed stable isotopes of C14 and N15

  9. Higher values --> Higher concentration of heavy isotope --> Higher trophic level Stable isotope analysis

  10. Estimate trophic position relative to algal baseline Stable isotope analysis

  11. Estimate trophic position relative to algal baseline Increase of 3.4 δ15N = 1 trophic level Stable isotope analysis

  12. Estimate trophic position relative to algal baseline Increase of 3.4 δ15N = 1 trophic level Stable isotope analysis 2° consumer 2° consumer 1° consumer 1° consumer 1° producer 1° producer

  13. 3° consumer all fish p << 0.05 2° consumer Trophic position of fishes varies across sites 1° consumer 1° producer

  14. Trophic position of fishes varies across sites 3° consumer all fish p << 0.05 2° consumer 1° consumer 1° producer

  15. Trophic position of fishes varies across sites 3° consumer all fish p << 0.05 2° consumer 1° consumer 1° producer

  16. Trophic position of fishes varies across sites 3° consumer all fish p << 0.05 2° consumer 1° consumer 1° producer

  17. Trophic position of fishes varies across sites 3° consumer all fish p << 0.05 2° consumer 1° consumer 1° producer

  18. Trophic position of fishes varies across sites 3° consumer all fish p << 0.05 2° consumer 1° consumer x x x x 1° producer

  19. Trophic position is reduced in absence of leathersides

  20. Habitat is suitable for leathersides

  21. Is this a true reduction in overall food chain length?

  22. True reduction in food chain length? Need info on predators 3° consumer 2° consumer 1° consumer 1° producer

  23. True reduction in food chain length? Need info on predators 3° consumer 2° consumer 1° consumer 1° producer

  24. True reduction in food chain length? Need info on predators 3° consumer 2° consumer 1° consumer x x x x 1° producer

  25. True reduction in food chain length? Need info on predators 3° consumer 2° consumer 1° consumer x x x x 1° producer

  26. Estimated reduction in food chain length x

  27. Ecosystem productivity Ecosystem size Theory explaining food chain length Food Chain Length Disturbance McHugh et al. EcolLett 2010

  28. Ecosystem productivity Ecosystem size Theory explaining food chain length Food Chain Length Disturbance McHugh et al. EcolLett 2010

  29. Ecosystem productivity Ecosystem size Theory explaining food chain length Food Chain Length Disturbance McHugh et al. EcolLett 2010

  30. fish fish predatory insects Changes in trophic level can indicate disturbance Food Chain Length Food webs herbivorous insects herbivorous insects Algae Algae Competitive exclusion of leathersides by redsides in disturbed, simplified systems? Disturbance Food Chain Length Disturbance McHugh et al. Ecol. Lett. 2010

  31. Intermediate predators occur at leatherside sites (but not quantitative samples) 3° consumer 2° consumer 1° consumer x x x x 1° producer

  32. Trophic position of fishes is higher at sites containing northern leatherside chub. Not explained by differences in habitat. Not explained by ecosystem size. Potentially explained by loss in intermediate trophic level, caused by disturbance. Preliminary conclusions

  33. Acknowledgements Luke Schultz and crew Craig Amadio Jason Luginbill Dave Zafft Pete Cavalli John Henderson Annie Hancock Brian Hale Allystair Jones Kayla Melling Sage Kelley Brent Hutchinson Peter Meyers Ryan Quinton Eric Mattson Eric Billman Matt Terry Ali Tippetts Funding and permits - Bureau of Land Management - Utah Department of Natural Resources - Wyoming Game and Fish

  34. Is algae a good baseline? Mountain sucker r2 = 0.73, p = 0.0308 Redside shiner r2 = 0.56, p = 0.0206 YES Speckled dace r2 = 0.55, p = 0.0216 Aquatic insects r2 = 0.67, p = 0.0067

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