1. Analysis of Walleye Growth, Movement and Habitat Quality in Lake Erie, 1990-2001 1 Wang, H.-Y., 1 Rutherford, E.S., 2 Haas, R.C., and 3 Schwab, D. J. Lake Erie Committee Annual Meeting 3/25/2003 Funded by Great Lake Fisheries Commission

2. Lake Erie Bathymetry Map

3. Objectives To explore walleye growth, movement and habitat quality in Lake Erie using tagging data, bio-data, catch rate data analyses, and bioenergetics modeling. Hypothesis Walleye migrate to areas of high growth rate potential (GRP) and grow faster there.

4. Tag Recovery Location Map (1990-2001) Boundary of basins (Ludsin, S.A. et al, 2001)

5. Walleye Biological Data From Ontario MNR Surveys, 1987-2001.

6. Commercial CPUE Patterns (1999) in ON Waters

7. Sport CPUE Patterns (1999) in U.S. Waters

8. 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 NOAA CoastWatch Data: Lake Erie Water Surface Temperatures, August 1992-2001

9. Forage Fish Density Index U.S. Agency Trawl SurveysOMNR Gillnet Surveys

10. Methods Movement - Map and model spatial pattern of commercial and sport CPUE by month and year. - Analyze tagging data by stock, and explore distribution of recapture locations. Growth - Estimate growth rate and length at 50% mature from bio-data. - Walleye Bioenergetic Growth Model.

11. Commercial CPUE patterns (1999) indicate that walleye migrate to EB in June, and migrate back to WB in September

12. Ordinary Kriging of Commercial CPUE in May-Nov, 1999

13. Most (78%) Recaptured Walleye were from 5 Tagging Sites in WB and 1 Site in EB

14. Large Walleye Tagged in WB were recaptured in CB and EB; EB-tagged Walleye Don’t Migrate

15. Walleye Recaptured in CB and EB Were Larger, Regardless Where They Were Tagged

16. Growth Rates of Age-2 and Older Walleye Appear Fastest in Eastern and Central Basin

17. WB Walleyes Mature at larger size than in EB. Females Mature at larger size than Males.

18. Walleye Bioenergetic Growth Model Estimate growth based on lake temperatures and prey densities. Assume Higher growth rate indicates better habitat quality

19. Walleye Growth Model Framework Growth = Consumption - Losses (Losses = Respiration, Egestion, Excretion) Consumption is a function of temperature, walleye weight and prey fish density

20. Gillnet CPUE Indicates Spatial Overlap is High Between Walleye and Clupeid Forage

21. Walleye Growth Model Predictions Correlate with Walleye Movement patterns, but not with Commercial CPUE data.

22. Results Walleye in the EB and CB appear to grow better and mature at smaller sizes than in the WB. Mostly large, female walleye migrate from WB to EB. Why??? Perhaps to increase fitness, i.e. increase female growth and fecundity.

23. Future Work Refine Walleye Growth Model using CPUE data on depth and temperature where walleye forage. Examine effects of decadal (1990-2001) changes in walleye density on walleye growth and movement.