The return of self-sustaining lake trout populations in Lake Michigan is a long-standing rehabilitation goal of the Illinois Department of Natural Resources (IDNR) Division of Fisheries and the Great Lakes Fishery Commission. Annual stocking of juvenile lake trout at sites lakewide since 1965 has largely resulted in minimal success until recently. Patterson et al. (2016) evaluated Illinois’s fall spawning assessment data and found similar abundances of mature lake trout in recent years at unstocked Waukegan Reef compared to Julian’s Reef, the only site within southern management units stocked annually. This result, along with findings of high relative catches (~50%) of unmarked ‘wild’ lake trout adults at both reefs in recent years has prompted the need for fall spawning assessments at additional offshore reefs in Illinois waters of Lake Michigan. Identifying and monitoring previously unsampled lake trout spawning sites is critical for developing effective stocking and harvest regulations for this important, native sport fish. Attaining geo-referenced bathymetry data and developing accurate maps of potential spawning reefs is an essential next step facilitating the planning and implementation of lake trout spawning assessments at unsampled reefs in Illinois. Thus, the objectives of this project were to 1) document the location and extent, 2) collect bathymetry data, and 3) create contour and three-dimensional bathymetric maps of five offshore reefs in Illinois’ portion of Lake Michigan. Results of this project will aid IDNR in measuring the extent of lake trout rehabilitation success and identify important potential spawning habitats that may be targeted for future protection and/or enhancement.
|Name||INHS Technical Report 2019 (04)|