Frequently Asked Questions
Isle Royale siscowet lake trout
Identifying siscowet lake trout spawning sites at Hawk Island, Lake Superior, using acoustic telemetry
May 2018 - December 2022
Lake trout (LT) recovery programs in the lower Great Lakes have focused on shallow-water, lean LT but now are broadening their management options to consider reintroduction of deep-water forms (e.g., humper introductions in Lake Erie). Lake Superior is the only Laurentian Great Lake with native populations of deep-water LT forms for introduction. Spawning sites of lean LT are well characterized but are unknown for deep-water LT. In a 2-year study of the reproductive life histories of LT orphotypes in waters surrounding Isle Royale National Park (IRNP), Lake Superior, the PIs identified the first potential spawning area for spring and fall spawning deep-water siscowets, located near Hawk Island (Goetz et al. 2017-Trans. Am. Fish. Soc. 146:268-282). We propose to deploy a positional acoustic telemetry array to discover where and when in this area spawning most likely occurs by observing the 2D movement of tagged siscowets in the spring and fall over a four-year period. The PIs have used this technology previously to identify lean LT spawning sites in the Drummond Island Refuge-Lake Huron and Thunder Bay. Sites identified were as small as 100 m2 and contained some substrates that would not previously have been considered suitable for spawning. Locating and describing the use of siscowet spawning sites will provide a means to obtain gametes of both spring and fall spawning siscowets for stocking purposes and will characterize spawning habitats for deep-water LT forms. This information can be used for introductions of deep-water LT forms in the lower Great Lakes to determine if spawning sites with similar characteristics are present and suitable for natural reproduction. It would also provide valuable information for mangers in Lake Superior to help understand the production dynamics of siscowets; currently the largest LT biomass in Lake Superior and the focus of a possible targeted fishery for omega 3 fatty acids.