An Overview of the Decline and Rehabilitation of Lake Trout in the Great Lakes

Lake trout (Salvelinus namaycush), were the principal keystone predator throughout most of the Great Lakes, and contributed to valuable commercial fisheries during the last century.   The combined effects of the invasion of the parasitic sea lamprey (Petromyzon marinus) and over fishing extirpated most population throughout the Great Lakes by the late 1950s.  Controls on fisheries, and reductions in sea lamprey numbers through chemical treatments of larvae in streams in the 1960s, offered the possibility of reintroductions to rebuild populations through stocking.   Managers thought that this was all that was required to restore populations to self-sustainability but success outside Lake Superior has been minimal.  Changes in the pelagic forage base from native to non-native species, additional invasions of non-native inverebrates, performance of stocked fish, and continued harvest have presented potential bottlenecks to wild recruitment.   This presentation will provide a broad overview of the progress made in each Great lake and challenges that remain, hence providing a baseline for the detailed cases histories that will follow in the symposium.