Restoration of Lake Trout in Lake Superior through Interagency Cooperative Management
Michael J. Hansen and Charles R. Bronte
Abstract.—The Lake Trout Salvelinus namaycush is a keystone species in the Laurentian Great Lakes that supported valuable fisheries throughout the basin until the 1950s. However, Lake Trout populations declined to near extirpation in nearly all of the lakes by the 1960s because of the combined effects of overfishing, Sea Lamprey Petromyzon marinus predation, and habitat degradation. To restore self-sustaining Lake Trout populations in Lake Superior, state, provincial, federal, and tribal agencies agreed to an interjurisdictional management framework that allowed them to articulate and institute (1) clear and common goals and actions for recovery, (2) early and intensive lakewide stocking of hatchery-reared Lake Trout to enhance failing stocks, (3) early and effective lakewide controls on mortality caused by Sea lampreys and fisheries, and (4) standardized lakewide evaluations of population trajectories and performance. Stocking was initiated in Lake Superior in 1950 and expanded after 1953, prior to effecting Sea Lamprey or fishery controls, thereby introducing large numbers of hatchery-origin fish that grew to maturity shortly after mortality was reduced. Abundant suitable nearshore spawning habitat was widely available for naive lean hatchery-origin Lake Trout, and native lean Lake Trout persisted in some areas. The Sea Lamprey-selective pesticide TFM (3-trifluoromethyl-4-nitrophenol) was applied first in Lake Superior in 1958 because of the presence of remnant native Lake Trout populations, which set the stage for closure of fisheries and good survival of newly stocked and remnant wild fish. As a consequence of these four factors, stocked fish exceeded historical density of wild fish by the 1980s in many areas and thereby generated enhanced reproductive potential when combined with remnant wild fish. Lake Trout recovery in Lake Superior is an extraordinary example of agency cooperation toward a common goal for managing recovery of an ecologically important shared resource.