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Coordination Workshops Concerning Early Mortality of Lake Trout in the Great Lakes
Travis O. Brenden1, Ji X. He2
1 Quantitative Fisheries Center, Michigan State University, 153 Giltner Hall, East Lansing, MI 48824
2 Alpena Fisheries Research Station, Michigan Department of Natural Resources and Environment, 160 E. Fletcher St., Alpena, MI 49707
Two workshops were convened that brought together fishery researchers and biologists from across the Great Lakes basin to discuss the current state of knowledge regarding early mortality of lake trout and how low survival rates in some lakes may be impeding the transition to self sustaining populations. The first workshop was held in October 2008 and consisted of a total of 22 presentations that summarized current understanding of lake trout ecology and population dynamics across the lakes. In addition, a discussion session was held for the purpose of synthesizing presented information and to propose answers, new ideas, or new questions regarding early mortality of lake trout and how it is influencing lake trout populations in the Great Lakes. Through this discussion session, it became apparent that providing answers as to what factors were causing low survival rates would be difficult given the wide-spread environmental changes that most of the lakes have undergone; as well, it would be difficult to evaluate stocking or management strategies for increasing survival of early life stages of lake trout as it is not clear how relevant previous research findings are given the environmental changes that have occurred. The consensus among the participants of the first workshop was that it would be advantageous if the second workshop was devoted primarily to brainstorming and discussing possible research projects to answer lingering questions regarding differences in survivability and ecology of both stocked and wild lake trout. The second workshop was held in April 2010 and, as requested, was devoted to brainstorming and discussing potential research areas. The five areas of research that were primarily discussed by participants of the second workshop were to: 1) conduct across-lake comparison of differences in survival of stocked fry, fingerlings, and yearling, 2) assess behavior and mortality of lake trout immediately after stocking, 3) evaluate how modifications to rearing environments might increase survival rates of stocked fish, 4) compare diets of wild and hatchery lake trout diets and physiological differences between wild and hatchery fish that might be influencing their feeding (e.g., gillraker spacing), 5) conduct hatchery-based evaluations of lethality limits of early life stages of lake trout and of bioenergetic model inputs.