Restoration of Native Lake Trout in Lake Superior, 1959-2012: A Case Study

Lake trout (Salvelinus namaycush) is the dominant predator in Lake Superior and experienced a lakewide stock collapse in the mid-1900s. The collapse was attributed to overfishing and sea lamprey (Petromyzon marinus) predation. Remnant off-shore stocks of three lake trout morphotypes survived from which to start the restoration process. Subsequent, binational agreement resulted in a primary restoration target of a sustained annual yield of 4 million pounds and secondary goals of restored recruitment via stocking and decreases in total mortality to levels allowing rehabilitation. Management actions taken included aggressive sea lamprey control, rehabilitation stocking of native strain lake trout, and regulation of commercial and recreational fisheries. These actions have resulted in increases in natural reproduction sufficient to justify cessation of stocking in most management units and significant reductions in lamprey mortality leading to increased abundance of wild lake trout approaching historical levels.  Progressively declining growth rates also indicate that lake trout populations may be at or approaching density-dependent levels. Ongoing challenges include 1) sustaining reductions in lamprey mortality and 2) achieving consistent reductions in fisheries harvest. Although work continues to meet these challenges, successful rehabilitation of lake trout in Lake Superior is a fishery management success story.