1. Do hypoxia- and temperature-induced changes in habitat use affect fish abundance and quality? Kevin L. Pangle (Central Michigan University), Paul J. Hurtado (MBI; OSU), Yuan Lou (OSU), Elizabeth A. Marschall (OSU), Daniel K. Rucinski (LimnoTech), Dmitry Beletsky (University of Michigan), Stuart A. Ludsin (OSU)

2. Goal Explore the population consequences of how thermal stratification & hypoxia affect growth & survival of pelagic fishes.

3. Thermal Stratification Rabalais, Turner & Wiseman (2002) creates environmental heterogeneity drives vertical distributions & habitat use. How? Thermal stratification hypoxia Vanderploeg et al (2009) Temp DO ZP Fish

4. Nutrients (N, P) Phytoplankton Bacteria Hypoxia Excess Nutrients Hypoxia

5. Coutant (1987)

6. Study System: Lake Erie Canada USA Warm epilimnion West Central East Cool Low oxygen Cool hypolimnion (becomes hypoxic)

7. Vanderploeg et al (2009)

8. Zooplankton Benthic Macroinverts. Walleye (www.buckeyeangler.com) Planktivorous Fish Benthivorous Fish Emerald shiner (www.cnr.vt.edu) Rainbow smelt (nas.er.usgs.gov) Yellow Perch (©Shedd Aquarium) White Perch (www.cnr.vt.edu) Piscivorous Fish Brandt et al. Central Lake Erie Food Web

9. –Direct mortality Sessile benthic organisms more affected than mobile organisms Mobile pelagic species can be susceptible –Sub-lethal effects → more likely for mobile species Caused by reduced access to optimal temperature, prey or refugia Atlantic Menhaden (Narragansett Bay) (www.geo.brown.edu) Gulf Menhaden (N. Gulf of Mexico) (www.leeric.lsu.edu) An “island” of dead menhaden Hypoxia effects on fish?

10. Modeling Approach Mechanistic Model: behavior/movement, physiology, ecology. GrowthSurvival Physical Environment (Temperature, Dissolved Oxygen) Sub-lethal consequences: growth (fish mass; w) Direct consequences: survival (# of fish; N) Movement # of fish N fish mass w

11. Physical Environment (1987-2005) Rucinski et al, 2010 “Bad”

12. Annual Variation (1987-2005) o

13. o

14. Modeling Approach Mechanistic Model: behavior/movement, physiology, ecology. GrowthSurvival Physical Environment (Temperature, Dissolved Oxygen) Sub-lethal consequences: growth (fish mass; w) Direct consequences: survival (# of fish; N) Movement # of fish N fish mass w

15. Q1Q1 Q2Q2 Q3Q3 Q…Q… Q 24 Movement Model Water column divided into 24 “patches” each roughly 1 meter deep. Q i = quality of patch i N i = # fish in patch i N1N1 N2N2 N3N3 N…N… N 24 Leave based on “patch” quality N1N1 N2N2 N3N3 N…N… N 24 Redistribute Movement Rule: Quality = GRP x Survival Q i = (G i -G min ) x (1/ μ i )

16. Predation, low DO, high Temperatures, “other”: Mortality Rate (μ) Dissolved Oxygen (ppm) Temperature ( ⁰ C)

17. Predation, low DO, high Temperatures, “other”: Predation (by Walleye) depends on light, attack rates, response rates, success rates. Hypoxia: Temperature : Thornton & Lessem curve (BEM) Other: Mortality Rate (μ)

18. General Model GrowthSurvival Physical Environment (Temperature, Dissolved Oxygen) Movement # of fish N fish mass w

19. CoolWarm

20. CoolWarm

21. Results: 1987-2005 (Aug-Oct) Population Size

22. Results: 1987-2005 (Aug-Oct) Growth Rate

23. Results: 1987-2005 (Aug-Oct) Mortality Rate 1994

24. Results: 1987-2005 (Aug-Oct) Refugia Low MortalityHigh Mortality

26. Concluding Remarks Summary Warming and hypoxia negatively impact pelagic fish: ↓Survival (direct) ↓ growth (indirect) ↑ aggregation/density Model captures key interactions affecting growth & survival Allows us to quantify contributions from many factors Directly explore causal relationships Applicable to other species

27. Concluding Remarks Management Implications Meso-scale (~1m) environmental factors may have big effects! Refugia during hypoxic events – hard to measure/predict Information gaps? Mortality model, movement rules, refugia Next steps Horizontal movement? Sources of mortality? Fish with other natural histories? Thermal preferences? Feedback via trophic interactions? Disease risk?

28. Questions?