In the northern hemisphere there are lakes that contain lake trout (salvelinus namaycush) populations with subgroupings referred to as morphotypes or ecotypes because they differ in their body and…

The University of Wisconsin System, through its Office of Sponsored Programs Division at the University of Wisconsin-Milwaukee (UWM), was awarded a $239,461.00 Project Grant by the U.S. Department of the Interior Fish and Wildlife Service Region 3 under the Fish and Wildlife Management Assistance program (CFDA 15.608). The objective of this 3-year grant is to determine the lake trout ecotypes present on Klondike Reef in Lake Superior and assess if they are in spawning condition. This research will support the restoration of diverse lake trout populations in the Great Lakes. UWM will partner with Purdue University to sample the reef, analyze fish size, age, body shape, lipid content, stable isotopes, and reproductive status, and conduct genomic sequencing to identify the ecotypes. The findings will guide the development of new lake trout broodstocks for stocking programs to fully re-establish native lake trout communities in the region.

In the northern hemisphere there are lakes that contain lake trout (salvelinus namaycush) populations with subgroupings referred to as morphotypes or ecotypes because they differ in their body and head shape as well as the habitats they live in. Lake superior, one of the laurentian great lakes, contains at least four lake trout ecotypes referred to as leans, siscowets, humpers, and redfins. Besides looking different, these ecotypes occupy different depths siscowets and humpers living in deeper water and leans and redfins being shallow. Some of the differences among the ecotypes are genetically based and, therefore, would be heritable and passed from one generation to another. In the early 1900S, most lake trout populations in the laurentian great lakes were either extirpated or greatly reduced because of overfishing and lamprey parasitism. However, over the past 50 years there has been stocking in all the great lakes to TRY and RE-establish lake trout. Recovery of lake trout has primarily focused on the lean ecotype in nearshore waters with little effort directed towards deeper, offshore areas historically inhabited by deep-water lake trout like siscowet and humpers. Full restoration of lake trout in the great lakes will require a complete complement of ecotypes adapted to varying depths in the ecosystem. Reestablishment of a deep-water ecotype of lake trout is a key component to restoring the health and sustainability of the native fish communityand has been identified in the lake wide rehabilitation plans developed by state, tribal and federal agencies in the great lakes. Lake superior has the only native, non-lean ecotypes in the laurentian great lakes. In the past, non-lean broodstocks were produced for stocking from eggs and sperm collected from lake trout on klondike reef, part of the caribou island reef complex in lake superior. While relatively little is known about this reef, IT appears to contain at least three lake trout ecotypes leans, humpers, and siscowets. Based on observations made during broodstock gamete collections, IT is likely that the broodstocks generated from klondike reef and used for restoration, were not a pure, single ecotype but a mix of ecotypes. Broodstocks generated from klondike reef are not currently held in hatcheries but are being requested now by managers for restoration and, therefore, new broodstocks need to be produced. In the future as broodstocks are developed from klondike reef, IT is essential to assess what potential lake trout ecotypes are present and reproducing on the reef that could contribute to the gametes being collected. IT is possible that managers may want to produce pure ecotype broodstocks or hybrids of different ecotypes. Regardless, a full characterization of the ecotypes atklondike reef and their reproductive timing will help guide managers and hatchery personnel in the development of new lake trout broodstock lines for great lakes lake trout restoration. The overall objective of this study is to determine which lake trout ecotypes are present on klondike reef during the fall (when gamete collection occurs) and if they are in spawning condition. To accomplish this, fish will be sampled on the reef at two times between september and october using gillnets. The size, age, body and head shape, lipid content, stable isotope ratio (indirect measure of their diet), andstage of reproduction will be assessed for all fish that are collected. Genomic tissue from a subsample of the fish will be sequenced to determine possible genetic differences and, together with the other measurements above, will be used to assign fish to different ecotypes. IT is difficult to define lake trout ecotypes based solely on appearance and, therefore, our goal is to use multiple metrics to more accurately accomplish their identification and to provide tools for managers to discriminate between ecotypes in future broodstock gamete collection on klondike reef.