Manuscript Report No. 04-01 PIKE AND WALLEYE IN THE ROCKY LAKE- ROOT-READER MARSH COMPLEX by Walt Lysack 2004 Manitoba Water Stewardship Fisheries Branch TABLE OF CONTENTS DESCRIPTION AND HISTORY OF THE STUDY AREA ................................................ 4 ROOT – READER PIKE STUDY..................................................................................... 7 ROCKY LAKE FISH STOCK MONITORING PROGRAM ............................................. 24 ROCKY LAKE CREEL SURVEY................................................................................... 29 DISCUSSION................................................................................................................ 39 ACKNOWLEDGEMENTS ............................................................................................. 52 REFERENCES.............................................................................................................. 53 LIST OF TABLES Table 1. Rocky Lake’s water chemistry during the 1980s. ............................................ 19 Table 2. Daily angling duration parameters................................................................... 32 Table 3. Parameters of fishing effort and catches of pike, walleye and bass ................ 33 Table 4. Parameters of CUE, no. fish angler hour ................................................... 34 Table 5. Parameters of individual pike and walleye weights ......................................... 35 Table 6. Parameters of kept walleye CUE reported on the creel survey forms. ............ 36 Table 7. Parameters of walleye abundance and yield................................................... 50 LIST OF FIGURES Fig. 1. Rocky Lake........................................................................................................... 6 Fig. 2. Root-Reader Marsh.............................................................................................. 7 Fig. 3. Water temperatures at station 1 in 2002. ............................................................. 8 Fig. 4. Water temperatures at station 3 in 2002. ............................................................. 9 Fig. 5. Water temperatures at station 5 in 2002. ........................................................... 10 Fig. 6. Water temperatures at station 7 in 2002. ........................................................... 11 Fig. 7. Temporal changes in flow velocity through the fishway in 2002......................... 12 Fig. 8. Temporal changes in flow velocity through the fishway in 2003......................... 13 Fig. 9. The increase in flow velocity from the top to the bottom of the fishway in 2002. 14 Fig. 10. DO and water temperature relationship............................................................ 15 Fig. 11. Temporal changes in DO.................................................................................. 16 Fig. 12. DO during late autumn and winter of 2002-2003.............................................. 17 Fig. 13. Spatial distribution of DO from May to September 2002. ................................. 18 Fig. 14. Temporal changes of pike ages in 2002........................................................... 20 Fig. 15. Temporal changes in pike sizes passing through the fishway in 2003. ............ 21 Fig. 16. Variability of CUE among gangs in 2003.......................................................... 21 Fig. 17. Growth of pike. ................................................................................................. 22 Fig. 18. Seasonal changes in age composition of pike in the Root-Reader marsh. ...... 22 Fig. 19. Changes in pike prey with increasing pike size. ............................................... 23 Fig. 20. Size distribution of Root-Reader pike in 2003. ................................................. 24 Fig. 21. Temporal abundance changes in Rocky Lake's fish species. ......................... 25 Fig. 22. Comparative growth of Rocky Lake's fish species. .......................................... 26 Fig. 23. Changes in Rocky Lake's walleye age compositions from 1981 to 1999. ........ 27 Fig. 24. Increase in maturity rate of Rocky Lake's walleye females. ............................. 28 Fig. 25. 1999 size distribution of Rocky Lake's pike and mature frequencies. .............. 29 Fig. 26. Total numbers of boats and anglers on Rocky Lake. ....................................... 31 Fig. 27. Walleye, pike and bass CUE in 2002. .............................................................. 32 2 Fig. 28. Weight distributions predicted from reported fork lengths. ............................... 35 Fig. 29. Distribution of kept :caught ratios of walleyes and pike from the creel survey.. 37 Fig. 30. Size distributions of walleye and pike angled from Rocky Lake in 2002........... 38 Fig. 31. Comparative growth and maturity of Wekusko Lake fish.................................. 40 Fig. 32. Frequencies of pike body sizes in Wellman Lake............................................. 41 Fig. 33. Pike and walleye sizes caught by anglers on Cormorant Lake......................... 42 Fig. 34. Pike sizes in Cranberry Lake............................................................................ 43 Fig. 35. The change from dominance by large pike on Asean Lake.............................. 44 Fig. 36. Size distribution of pike caught by anglers on Reed Lake. ............................... 45 Fig. 37. Pike size distribution in Wekusko Lake. ........................................................... 46 Fig. 38. Length frequency distributions of pike in 8 Minnesota lakes. ........................... 47 Fig. 39. Size frequencies of Cedar Lake pike................................................................ 48 Fig. 40. Size distributions of Southern Indian Lake pike................................................ 49 Fig. 41. Effect of growing season on walleye fecundity................................................. 50 Fig. 42. Walleye yield distribution.................................................................................. 51 3 PIKE AND WALLEYE IN THE ROCKY LAKE - ROOT-READER MARSH COMPLEX DESCRIPTION AND HISTORY OF THE STUDY AREA Rocky Lake and the Root-Reader Marsh are located about 30 km. north of The Pas, Manitoba, Canada (Fig. 1). The surface area of Rocky Lake is 10968 ha. Rocky Creek drains from the southern bay of Rocky Lake, flows through the control structure into Root Lake, continues into Reader Lake and eventually reaches the second control structure on Whitefish Creek at its junction with the Saskatchewan River. The Root- Reader Marsh is part of the Saskeram Marsh WMA, Wildlife Management Area, that also includes the Carrot River Triangle. This WMA includes 95,812 ha. of crown land along the Saskatchewan River Delta. It was designated as a Wildlife Management Area in 1963 to mitigate the loss of wildlife habitat due to the Grand Rapids Dam at the end of the Saskatchewan River. The original Rocky Creek water control and fishway were built in 1947 by DUC, Ducks Unlimited Canada. The purpose of this structure was to ensure that Root and Reader Lakes had a consistent water supply. This structure also prevented more than 1,800 acres of wetlands upstream of the dam from drying out in years of low precipitation. The structure was built with the full cooperation of the provincial government that assumed operational responsibility for this and several other water controls built by DUC in The Pas area. These water control structures improved muskrat and waterfowl production. In 1974, DUC replaced the original wooden structure and fishway. The current structure was built in 1991 with the cooperation and approval of the provincial government. Manitoba’s Fisheries Branch and the federal Department of Fisheries and Oceans both approved its design. During the history of water control structures on Rocky Creek, there have been occurrences of fishkills in the winter. Winter fishkills are typically due to insufficient DO, dissolved oxygen. Deoxygenation of water occurs naturally in shallow water wetland systems. The water control structure is situated in the natural outlet channel and regulates the flow of water from Rocky Lake into the Reader and Root Lake marshes. Excess water from the system is released into the Saskatchewan River through the South Reader outlet at Whitefish Creek. If the water control structure were not in place, the natural "spill" elevations of Rocky and Reader Lakes would allow the present water level in Rocky Lake to drop approximately 1.2 meters. This would reduce Root and Reader Lakes to a series of small shallow basins resulting in a loss of more than 11000 ha. (27000 acres) of flooded wetland habitat that is utilized by waterfowl and other local wildlife. The Rocky Creek control structure: 1. maintains the water level of Rocky Lake within a prescribed range based on historical water levels that generally satisfies the needs of various groups including cottage owners, lodge owners and commercial bait fishers. 2. allows DUC to use Rocky Lake as a storage reservoir from which water can be drawn to maintain healthy wetland habitat in Root and Reader Lakes. 3. provides fish passage for pike and other species of fish that move between Rocky Lake and Root and Reader Lakes. 4 4. maintains wetland habitat immediately upstream of the water control structure and provides a consistent water supply to the three lakes (Bignell, Watseskwatipi and Keaskeskak) south of Rocky Lake. 5. provides flood and drought protection to Rocky, Root