Genetic Heritage of Naturally Produced Lake Trout in Lake Michigan

Lake Trout (Salvelinus namaycush) restoration efforts in Lake Michigan have relied on the propagation and stocking of six hatchery strains: Seneca Lake, Lewis Lake, Green Lake, Marquette, Apostle Island, and Isle Royale.  Lake Trout recently began reproducing and recruiting in southwestern Lake Michigan at low levels, and suggests some progress toward restoration goals.  Determining which strains have contributed to the observed natural reproduction will help guide future stocking efforts.  Our objectives were to 1) identify a subset of microsatellite markers that reliably delineate strain of origin for the six Lake Trout strains stocked into Lake Michigan, and 2) determine if the genetic markers and reference data are capable of diagnosing the genetic heritage of interstrain crosses and wild caught Lake Trout.  Thirty previously developed microsatellite loci were used to delineate the six reference strains using program STRUCTURE.  One thousand individuals were simulated for all possible combinations of F1 pure and interstrain crosses (21 total crosses; 21,000 simulated offspring).  Strain of origin of all simulated individuals was estimated using STRUCTURE, and the reference data were used to assess genetic heritage of wild caught Lake Michigan Lake Trout to evaluate the reproductive success of the hatchery strains used for restoration.