STATUS OF WALLEYE IN THE GREAT LAKES: CASE STUDIES PREPARED FOR THE 1989 WORKSHOP edited by Peter J. Colby Ministry of Natural Resources Fisheries Research Section, Walleye Unit 435 S. James Street P.O. Pox 5000 Thunder Day, Ontario, Canada P7C 5G6 Cheryl A. Lewis Ministry of Natural Resources Glenora Fisheries Station R. R. #4 Picton, Ontario, Canada KOK 2T0 Randy L. Eshenroder Great Lakes Fishery Commission 1451 Green Road Ann Arbor, MI 48105-2898 Citation (general): Colby, P. J., C. A. Lewis, and R. L. Eshenroder, [ED.]. 1991. Status of walleye in the Great Lakes: case studies prepared for the 1989 workshop. Great Lakes Fish. Comm. Spec. Pub. 91-l. 222 p. Citation (example for individual paper): Schram, S. T., J. R. Atkinson, and D. L. Pereira. 1991. Lake Superior walleye stocks : status and management, p. l-22. In P. J. Colby, C. A. Lewis, and R. L. Eshenroder [ed.]. Status of walleye in the Great Lakes: case studies prepared for the 1989 workshop. Great Lakes Fish. Comm. Spec. Pub. 91-l. Special Publication No. 91-1 GREAT LAKES FISHERY COMMISSION 1451 Green Road Ann Arbor, MI 48105 January 1991 The case studies in this publication were produced as preparatory material for the Walleye Rehabilitation Workshop held June 5-9, 1990 at the Franz-Theodore Stone Laboratory at Put-in-Ray, Ohio. This workshop was sponsored by the Great Lakes Fishery Commission's Board of Technical Experts. For a number of years, Henry H. Regier had urged the Board to initiate such a study to document recent changes in walleye populations that were particularly evident inwestern Lake Erie. A broad examination of walleye population changes in the Great Lakes was last undertaken at the Percid International Symposium held in 1976, and an update was very desirable. Peter Colby graciously agreed to chair the workshop for the Board and gratefully acknowledges the support of the steering committee: Carl Raker, Robert Haas, Joseph Koonce, Cheryl Lewis, Kenneth Mimms, and Terry Lychwick. Also very noteworthy were the contributions of Special Editor Wilbur Hartman and Associate Editor Gail Etter. R. L. Eshenroder December 6, 1990 Lake Superior Walleye Stocks: Status and Management, by S. T. Schram, J. R. Atkinson, and D. L. Pereira . 1 Walleye Rehabilitation in Lake Michigan, 1969-1989, by J. C. Schneider, T. J. Lychwick, E. J. Trimberger, J. H. Peterson, R. O'Neal, and P. J. Schneeberger.......................23 Rehabilitation of Walleye in Saginaw Bay, Lake Huron, by L. E. Mrozinski, J. C. Schneider, R. C. Haas, and R. E. Shepherd . 63 The Present (1989) Status of Walleye Stocks in Georgian Bay, North Channel, and Canadian Waters of Southern Lake Huron, by J. A. Reckahn and L. W. D. Thurston..................85 Walleye in Lake Erie and Lake St. Clair, by S. J. Nepszy, D. H. Davies, D. Einhouse, R. W. Hatch, G. Isbell, D. MacLennan and K. M. Muth.........................................145 The Resurgence of Walleye in Lake Ontario, by J. N. Bowlby, A. Mathers, D. A. Hurley, and T. H. Eckert.......................................169 References . 207 LAKE SUPERIOR WALLEYE STOCKS: STATUS AND MANAGEMENT S. T. Schram Wisconsin Department of Natural Resources P.O. Box 589 Dayfield, WI 54814 J. R. Atkinson Ontario Ministry of Natural Resources Fisheries Branch, Thunder Bay. Ontario, CANADA P7C 5G6 D. L. Pereira Department of Fish and Wildlife University of Minnesota, St. Paul, MN 55108 ABSTRACT. This paper describes the current status of walleye (Stizostedion vitreum vitreum) stocks in Lake Superior. Although Lake Superior is oligotrophic with a fisheries comprised primarily of cold-water species, walleye have played an important role in shallow-water areas and embayments. The western Lake Superior stock was lightly exploited until dramatic water quality improvements occurred in 1979. The stock now supports a popular sport fishery in both Wisconsin and Minnesota. The slow growth of this stock may make it extremely vulnerable to overexploitation. Other Wisconsin stocks are found in Kakagon Slough and the Bad River. Both stocks support sport and tribal fisheries and the use of supplemental stocking is being investigated. The three large stocks historically in Ontario waters include Nipigon Bay, Black Bay, and Whitefish Bay. All stocks are depressed and stocking is being used for rehabilitation. Overfishingwas identified as the primary reason for declining Lake Superior walleye abundance. Several potential, but undocumented, adverse impacts from exotic species are noted. Contaminant levels on largerwalleye have exceeded recommended consumption guidelines in several areas. Managers attempting to rehabilitate walleye stocks will have to determine basic population characteristics and identify sources of stress before developing a management plan. INTRODUCTION This paper reports on the current status of major walleye (Stizostedion vitreum vitreum) stocks in Lake Superior (Fig. 1). Lake Superior is classified as oligotrophic due to its low productivity and the glacial characteristics of its drainage basin (Lawrie and Rahrer 1972; Matheson and Munawar 1978). Among the Great Lakes, Lake Superior has the lowest summer surface temperature and mean annual lake temperature (Bennett 1978). Native fish are comprised primarily of cold-water species: 1) lake trout (Salvelinus namaycush), 2) lake herring, (Coregonus artedii), and 3) lake whitefish, (Coregonus clupeaformis). This community was severely depleted by the stresses of exploitation, exotic species, and habitat degradation (Lawrie 1978). Walleye and other cool-water species better adapted to shallow, mesotrophic systems have played an important but secondary role, both ecologically and in sport and commercial fisheries (Ryder 1968; Lawrie and Rahrer 1972). Walleye were historically harvested in shallow-water areas and discrete embayments (Nutte 1944; Ryder 1968; Pereira et al., Minnesota DNR, unpubl. data; Schram et al., Wisconsin DNR, unpubl. data). Maximum commercial harvests from U.S. waters were 56,000 kg obtained in Minnesota in 1885, and 170,000 kg from Ontario waters in 1966 (Fig. 2) (Baldwin et al. 1979). Lack of data on most Lake Superior walleye stocks limit analysis of stock problems. Some problems have been documented with biological data, while others are the opinion of local managers. The decline of stocks in Black Bay (Ontario) and in Michigan's waters were believed to be due primarily to overharvest (Schneider and Leach 1977; Colby and Nepszy 1981). Pollution and/or overexploitation played a major role in the decimation of the walleye in Nipigon Bay (Ryder 1968; MacCallum and Selgeby 1987). Exotic species such as rainbow smelt (Osmerus mordax) and sea lamprey (Petromyzon marinus) are present, but any adverse impact is unknown (Schneider and Leach 1977). Fig. 2. Lake Superior commercial walleye production, 1868- 1977 (Baldwin et al. 1979). STOCK INFORMATION Minnesota Minnesota shares a small walleye population in the Pigeon River with Ontario and shares the western lake Superior stock with Wisconsin. The Pigeon River population spawns in the Pigeon River but little else is known about its biology. In 1980, samples of fish over 394 mm exceeded the current action level for mercury as established by the U.S. Food and Drug Administration. There is a small tribal subsistence fishery on this stock (Steven Hirsch, Minnesota DNR, pers. commun.). Additional stock data were summarized by Ball (1988a). The western Lake Superior stock provides a high-quality sport fishery for anglers in the St. Louis River. This stock is discussed in detail in the Wisconsin section. Minnesota's walleye season extends from the second Saturday in May to February 15, with no size limit and a possession limit of six. Wisconsin Three walleye stocks inhabit Wisconsin waters: 1) western Lake Superior, 2) Kakagon Slough, and 3) Bad River. Each stock has experienced different levels of exploitation from sport and commercial fisheries. All stocks live primarily in Lake Superior or Chequamegon Bay and spawn in tributary streams. Commercial production during 1944-55 averaged 10,600 kg annually. Fearing overexploitation, anglers convinced the Wisconsin Conservation Commission to close the commercial fishery after 1955. In 1971, the Wisconsin Supreme Court removed control of tribal fisheries from the state to the Lake Superior Band of Chippewas. Beginning in 1972, the Bad River Band began gillnetting the spawning runs in the Kakagon Slough and Bad River. In 1980, an assessment fishery by the Red Cliff Band began on the western Lake Superior stock. Both Bands still continue their commercial and subsistence fisheries on these stocks. Contaminant monitoring has been conducted since 1970. Elevated mercury levels from walleye collected in 1984-85 prompted the issuance of a fish consumption advisory for Lake Superior and the St. Louis River. Currently, sport anglers have an open season with a daily bag limit of five, and no size limit. Western Lake Superior The western Lake Superior stock is one of the few Great Lakes walleye stocks to perpetuate over the past century. Survival is due to low exploitation rates prior to 1979. As early as 1900, water pollution in the St. Louis River from upstream paper mills had caused oxygen deficiencies and fish taste and odor problems associated with a variety of chlorophenolic products produced during the pulping process. A sport fishery occurred in the St. Louis River but harvest was limited by the water quality problems which gave fish a poor flavor. In 1978, the Western Lake Superior Sanitary District (WISSD) began treating domestic and industrial wastes from a 1,300 sq km area within the St. Louis River watershed. Much of these wastes were previously discharged into the river, including chloro-organics from upstream paper mills. Diversion of chloro-organics to WLSSD markedly improved the palatability of fish from the St. Louis River and increased angling pressure dramatically. Since 1979, the western Lake Superior stock has been subjected to increasing angler pressure. In response to a concern over possible adverse impacts from exploitation, the Wisconsin DNR initiated a comprehensive study of the western Lake Superior walleye stock in 1978 (Schram et al.