Evidence of Wild Juvenile Lake Trout Recruitment in Western Lake Michigan

Abstract

Lake Trout Salvelinus namaycush were extirpated from Lake Michigan by the early 1950s, and as part of an effort to restore naturally reproducing populations, hatchery‐reared fish have been stocked since the early 1960s. Stocked fish are marked with a fin clip to differentiate them from wild, lake‐produced Lake Trout; marking error for the 2007–2010 year‐classes of Lake Trout stocked by federal hatcheries averaged 3.0%. Egg deposition, emergent fry, and wild juvenile Lake Trout have previously been observed, but no sustained wild recruitment has been measured in assessment surveys or in sport and commercial fishery catches. In 2011 and 2012, we caught juvenile Lake Trout in gill‐net and bottom trawl catches that were targeting Bloater Coregonus hoyi in water depths greater than 80 m. Unclipped, wild Lake Trout represented 20% of all Lake Trout caught in a southern offshore region of Lake Michigan. In northwestern Lake Michigan wild recruits represented from 10% to 27% of the 2007–2009 year‐classes, and we recovered a small number of wild Lake Trout from the 2010 year‐class. This is the first evidence for consecutive year‐classes of naturally produced Lake Trout surviving beyond the fry stage in Lake Michigan.Received July 13, 2012; accepted November 26, 2012

Fatty‐acid profiles of juvenile lake trout reflect experimental diets consisting of natural prey

“…Mortality within the first year of life was identified as a major impediment to self-sustaining lake trout populations (Fisher et al, 1996;Bronte et al, 2008). With natural reproduction occurring at higher rates in recent years, a desire to assess foraging habits of wild-origin juvenile lake trout has emerged (Fitzsimons et al, 2010;Hanson et al, 2013;Lantry & Lantry, 2014). However, information on age-0 lake trout diet compositions in the Great Lakes is restricted to Lake Superior (Swedberg & Peck, 1984;Hudson, Savino & Bronte, 1995) and Lake Huron (Roseman et al, 2009).…”

Factors Affecting Postrelease Survival of Coded‐Wire‐Tagged Lake Trout in Lake Michigan at Four Historical Spawning Locations

“…High relative survival of fish stocked at Julian's Reef, the Southern Refuge, and Clay Banks, as well as attainment of a relatively high proportion (12–20%) of adults (age ≥ 9) at these locations, corresponds with recent modest increases in wild recruitment near the three locations (Hanson et al. ; Kornis et al ). This suggests that postrelease survival of stocked fish was adequate for producing the spawning stocks needed for wild recruitment, although Patterson et al.…”

“…), recruitment of wild age‐1 and older Lake Trout (Hanson et al. ; LMLTWG ), and aggregations of mature Lake Trout (age ≥ 7) above the recommended and adopted management benchmark (Bronte et al. ; Dexter et al.…”

An Exploratory Assessment of Thiamine Status in Western Alaska Chinook Salmon (Oncorhynchus tshawytscha)

“…Percent mean catch weighted diet composition (SD) of juvenile Chinook, coho, chum, and pink salmon in the northern Bering Sea (2009)(2010)(2011)2013 (25) 3 (2) 5 (3) ¹Thiaminase, + positive; -negative; Unk, unknown or not reported (Ceh et al 1964;NRC 1983;Zajicek et al 2005) ²2013 pink salmon diet data not available. ³Unidentifi able fi sh species lake trout reproduction can be seen with the recent increase in recruitment coinciding with egg thiamine concentrations exceeding 4 nmol·g -1 (Hanson et al 2013), however for full and normal recruitment, egg thiamine will need to be > 8 nmol·g -1 . Although the data are limited, egg thiamine levels appear consistent with productivity patterns observed in upper Yukon River Chinook salmon.…”