Historical Evidence for Discrete Stocks of Lake Trout (Salvelinus namaycush) in Lake Michigan

Abstract

Although few biological data exist on the now extinct native lake trout, Salvelinus namaycush, of Lake Michigan, historical records and interviews with former commercial fishermen strongly suggest that this once widespread resource was composed of a number of discrete spawning populations or stocks. A natural division of the resource into distinct stocks is consistent with the size of Lake Michigan and its varied physiography. The native trout may have undergone subtle genetic changes over the millennia, although we cannot determine whether the physical and behavioral differences represented different genotypes or only temporary effects of the local environment. Because of physiographic similarities among the upper Great Lakes and probable interchanges of lake trout during the last glacial period, we recommend that progeny of extant wild stocks, particularly from Lake Superior, are genetically most suitable for recolonizing Lake Michigan. Moreover, the hatchery-held parents of such fish should be infused periodically with genes of the wild or feral donor populations. Despite the sound historical basis for these recommendations, we also recognize that sufficiently high stocking rates coupled with a reduction of heavy exploitation may be even more important than heritability in obtaining self-sustaining populations.Key words: lake trout, discrete stocks, Lake Michigan, historical changes, phenotype, homing, extinction, planted strains, rehabilitation

Differentiation of deep-water lake charr Salvelinus namaycush in North American lakes

“…Our focus here is on resource polymorphisms involving deep-water lake trout. Distinctive shallowwater morphs of lake charr have been described for Great Bear Lake (Blackie et al 2003;Alfonso 2004) and have been reported from the Great Lakes (Brown et al 1981;Goodier 1981;Krueger and Ihssen 1995), but enough descriptive material for across-lake comparisons is lacking. The problem is with the Laurentian Great Lakes accounts, which except for the lean morph are sparse, consisting mostly of comments on color variations and generalized descriptions of shape (e.g., racers) (Goodier 1981).…”

Acoustic estimates of abundance and distribution of spawning lake trout on Sheboygan Reef in Lake Michigan

“…The southern refuge, known as the Mid-Lake Reef Complex (MLRC), comprises approximately 2859 km 2 of relatively deep reef habitat (40-80 m) including Sheboygan, East, Northeast, and Milwaukee reefs. The MLRC was historically productive as a spawning area (Brown et al, 1981;Dawson et al, 1997) and has received paired stockings of Marquette and Seneca strains of lake trout pursuant to the Lakewide Management Plan implemented in 1985 . Bronte et al (2007) found that Sheboygan and East Reefs had the highest spawner catch-per-effort of any spawning location sampled in 1999-2001, and Janssen et al (2006 have confirmed deposition of viable eggs and production of fry at these two locations in [2001][2002][2003][2004].…”

Fertilization of Eggs of Lake Michigan Lake Trout Salvelinus namaycush in Lake Water: Effect of PCBs (Aroclor 1254)

“…comm. 1994) and some of these fish are known to have spawned (Brown et al 1981, Holey et al 1995. Nevertheless, intensive interagency sampling efforts have only found evidence of lake produced yearlings or older offspring in a few places including Grand Traverse Bay (13 % and 7 % of the 1976 and 1981 year classes) and Platte Bay (4% of the 1983 year class) during 1983-1989(Rybicki 1991, for review: Holey et al 1995.…”