1. Regime Change in a Large River Fish Assemblage Mark Pyron Center of Aquatic Biology and Fisheries Environmental Science 2015 Wabash River Symposium

2. Collaborators: Dawn DeColibus Becca Logsdon Dave Weitzel Bob Mueller Jen Pritchett Jay Beugly Stephen Jacquemin Luke Etchison Michael Allen Mario Minder Jim Gammon Kevin Wyatt Jesse Becker Tom Lauer Allison Rober Indrajeet Chaubey Reuben Goforth Brent Murry

3. Topics Wabash River Body size analysis –Change with time Food web analysis

4. Wabash River 2nd largest trib of Ohio River 85,000 km 2 watershed 764 km long

5. History of Wabash River -1900: Abundant and diverse fishes

6. History of Wabash River pre-1900: Abundant and diverse fishes 1900 – 1974: point source pollution, agriculture, dam building

7. History of Wabash River pre-1900: Abundant and diverse fishes 1900 – 1974: point source pollution, agriculture, dam building 1974: Clean Water Act

8. History of Wabash River pre-1900: Abundant and diverse fishes 1900 – 1974: point source pollution, agriculture, dam building 1974: Clean Water Act 1974 – 2015: invasive species, nutrient and sediment reduction

9. Fish work: Jim Gammon collected 1968-98 Lauer & Pyron 2001-8

10. Jim Gammon began project 1968-98 500-m sites Boat electrofishing

11. Sampling Protocol: Electrofish 500 m

12. Collect all fishes Measure, release Sampling Protocol:

13. Gammon’s results: High diversity: 100+ species Recovering from pollution IBI scores improved

14. Longterm assemblage: body size analysis Convert size-abundance matrix into size bins Regress abundances against size bins

15. Examine organisms by size Convert size-abundance matrix into size bins Regress abundances against size bins Steeper with exploitation Steep regression = inefficient ecological transfer

16. Longterm assemblage: Steeper with exploitation 1974-93 1974-93 1994-2008

18. Trophic Groups Planktivores fishofohio.com Gizzard Shad miseagrant.umich.edu Silver Carp

19. Benthic invertivores tnfish.org ohiodnr.gov Trophic Groups Freshwater Drum Shorthead Redhorse Blue Sucker Planktivores fishofohio.com Gizzard Shad miseagrant.umich.edu Silver Carp

20. Benthic invertivores tnfish.org ohiodnr.gov Trophic Groups Freshwater Drum Shorthead Redhorse Blue Sucker Piscivores Spotted Bass ohiodnr.gov Longnose Gar tpwd.texas.gov Planktivores Gizzard Shad fishofohio.com

21. Changes in Trophic Groups

22. Regime shift ~ 1992 Persistent change in structure and function of a system Cause? Nutrients, invasive species, hydrologic alterations, climate change?

23. Time lag analysis: 1968-2008 Use only individuals > 162 mm SL (susceptible to boat electrofisher) Was there a large change in fish assemblages in mid-90s?

24. Redundancy Analysis Change in assemblage?

25. Species that drive RDA

26. Food Web Analysis Isotopes: 13C and 15N ratios Museum archives Pre-1992 vs Post -1992 –Piscivores –Benthic invertivores –Planktivores Mussels Fishes

27. Food web analysis: sofia.usgs.gov

28. Silver Carp consume pelagic detritus miseagrant.umich.edu Mean d13C Mean d15N

29. Mussels shifted sources Mean d15N

30. Gizzard shad and Minnows Mean d13C

31. Complete assemblage Mean d13C Mean d15N

32. Algal assemblage changed (gizzard shad stomachs) 2014 Water column

33. Food web changed from 1968-2008 Shift from pelagic to benthic carbon sources Causes? Changes in nutrients? Changes in algal assemblage; both?

34. Food web changed from 1968-2008 Decrease in N, Increase in P Correlated with increased benthic invertivores

35. Silver Carp fecal pellets transfer nutrients to benthic fishes Blue catfish increased growth Channel catfish survive

36. Silver Carp fecal pellets transfer nutrients to benthic fishes Blue catfish increased growth Shift nutrient source from pelagic to benthic habitat

37. Plankton consumed by Silver Carp: Algae Riparian C3 fecal pellets available to other consumers

38. Summary Switch in trophic group dominanceSwitch in trophic group dominance Planktivores to benthivoresPlanktivores to benthivores Silver Carp and Ag nutrientsSilver Carp and Ag nutrients Food web changes:Food web changes: Shift from pelagic to detritusShift from pelagic to detritus