LAKE TROUT REHABILITATION IN THE GREAT-LAKES - AN EVOLUTIONARY, ECOLOGICAL, AND ETHICAL PERSPECTIVE

We reviewed key features of the evolutionary biology of lake trout (Sa lvelinus namaycush) and their significance for rehabilitation programs in the Great Lakes. Despite repeated translocation. by glacial advanc es during the Ice Age (the Pleistocene) that eliminated most populatio ns, lake trout have genetic diversity comparable with other North Amer ican salmonines. Various embryological and adult features suggest lake trout had a long reproductive history in lakes, although river spawni ng may be a primitive feature of the species and may have been importa nt in glacial refugia. Observations that hatchery-reared lake trout se lect mostly mainland shoals for spawning in the Great Lakes are interp reted by us to be a result of evolution in smaller lakes where the mai n source of spawning gravels is shoreline erosion. We hypothesize that longevity in lake trout (a record among chars) may have evolved becau se of a near absence of predation on adults in contrast to predation o n juveniles that survived less well, in parr, because of cannibalism. Longevity, a physiological ability to colonize the coldest of waters d uring deglaciation, and an ecological role as a dominant piscivore in unperturbed systems all indicate that lake trout should fare best unde r conditions of low adult mortality and high biomass. Although the Gre at Lakes fish community is enriched compared with when lake trout popu lations were abundant or with where lake trout evolved, the species ha s the potential to suppress other fishes to its benefit. We provide ec ological and ethical reasons why lake trout rehabilitation should be a priority for the Great Lakes: lake trout are particularly suited for the deepwater food chain, they are the only salmonine (among those cur rently stocked in the lakes) that have the potential to become self-su staining at their current levels of abundance, and emphasis on stocked exotics reflects adherence to a scientifically obsolete philosophy of ''wise use'' that ignores evolutionary-ecological relationships. For fishery management we recommend greater use of genetic diversity and o f life stages capable of being imprinted, maintenance of high adult su rvivorship and biomass, and expanded communication with a wider array of clients. We also advocate lines of research that will test our mana gement recommendations, including assessing the implications of attemp ting to keep the Great Lakes fish community in an early stage of succe ssion.