Recovery of Saginaw Bay Walleye, Lake Huron
David G. Fielder and James P. Baker
Abstract.—Saginaw Bay is a large coolwater region of Lake Huron and Walleye Sander vitreus is the apex predator. From the time of first settlement to the mid-1940s, the bay’s Walleye population was the target of a loosely regulated commercial fishery characterized by periods of overharvest and recovery but was sustained for more than half a century at an average annual yield of about 495 metric tons. The fishery collapsed due to a series of year-class failures attributed to declining water quality, habitat degradation, and effects of invasive species. The degraded and collapsed condition lasted until the early 1980s. With improving water quality stemming from clean water legislation and the closure of the commercial fishery, a new period of improvement was achieved. Walleye fingerling stocking was implemented and a recreational fishery soon emerged. Research and assessment sought to monitor stock mortality, growth, and exploitation rates as well as contribution of stocked fish to the fishery. Recovery plans were drafted that sought to improve spawning habitat and improve survival of Walleye fry by creating a predation barrier to the predatory effects of the invasive Alewife Alosa pseudoharengus through increased Walleye stocking. A series of cascading food-web changes took place in Lake Huron, resulting in the sudden collapse of Alewives, and Walleye natural reproduction surged beginning in 2003. Walleye stocking was discontinued in 2006 and recovery targets were first achieved in 2009. Management and research shifted from recovery efforts to enhanced stock assessment efforts and modeling, a clear sign of success! Key lessons learned include (1) eliminating or at least reducing obstacles to reproduction (such as habitat and water quality) are essential first steps to laying the foundation for recovery, (2) maintaining populations (via of stocking in this instance) will help ensure that broodfish are available for spawning when conditions improve, (3) ecosystems are resilient and when released from stressors (Alewives in this instance) natural processes can resume, (4) great value exists in survey/assessment investment and long-term data sets for guiding restoration, and (5) resolve and commitment by natural resource professionals, administrators, and stakeholders is critical for sustaining restoration efforts and the investment they require.