The Genetic Legacy of Reintroduced Green Bay Muskellunge

Muskellunge (Esox masquinongy) were extirpated from Green Bay, Lake Michigan in the early 1900's.  Since 1989, the Wisconsin Department of Natural Resources have been active in reestablishing a Great Lakes strain of muskellunge in Green Bay.  No locally adapted remnant source populations exist for Green Bay.  Therefore, maximizing the genetic diversity of the founding populations while using Great Lakes derived sources has been a continual management goal.  Multiple source populations have been used in the 20+ years of restoration efforts.  Fertilized muskellunge eggs were originally imported to Wisconsin from the Indian River Spreads of Michigan (Lake Huron drainage) from 1989 through 1993 and from Lake Saint Claire in 1996; a total of 24-30 individual fish contributed gametes in these 6 years.  Recently, efforts have focused on using Georgian Bay (Lake Huron) spotted muskellunge.  To date, the restoration efforts have been a numerical success in Green Bay.  However, concerns exist as to the long-term sustainability of this success.  The objective of this study was to determine if the muskellunge population of Green Bay was founded by a combination of sources and how the current genetic diversity levels compare to extant inland populations of muskellunge and other Great Lakes muskellunge populations.  Samples of adult muskellunge from recreational fishermen and targeted sampling were genotyped using a suite of 14 microsatellite loci.  Additional populations from inland Wisconsin and elsewhere in the Great Lakes (including Georgian Bay, Lake St. Claire, and Buffalo River) were also surveyed.  Bayesian admixture analysis showed the current population in Green Bay was comprised of two distinct genetic lineages: an Upper Great Lakes lineage (Georgian Bay/Lake St. Claire) and an unconfirmed source that is likely consistent with the Indian River Spreads.  Allelic richness and heterozygosity were lower in the founding population than other populations of inland muskellunge.  The results of this work are being used to direct future broodsource choices.