Temporal stability of lake whitefish genetic stocks in Lake Michigan

Lake whitefish Coregonus clupeaformis are the predominant species in the Lake Michigan commercial fishing industry. Six genetic stocks were identified in Lake Michigan in 2007; however, genetic structure can fluctuate throughout time due to demographic variables and changing environments. Temporally stable genetic units have a higher probability of containing genetically adaptive traits and thus, are integral components of a sustainable stock-based management approach. The objective of this research was to determine if the genetic stock structure of lake whitefish in Lake Michigan has remained temporally stable from the 1970s through early 2007. Archived scale samples collected by state and tribal agencies during annual assessments from the 1970s, 1980s, and 1990s were used as a source of deoxyribonucleic acid (DNA). Samples were genotyped at 11 microsatellite loci consistent with the contemporary genetic stock dataset. Tests of FST, Jost's DEST, and Nei's genetic distance were used to compare nine historical sample populations to contemporary stocks. Most stocks showed temporal stability for a majority of the three different analysis methods. The only historical samples to not support the trend of temporal stability were located in the Green Bay region, where two genetic stocks are present in close proximity and are known to have relatively high levels of gene flow between the two stocks. The prevalence of temporal stability gives support to the theory that a stock-based management plan is appropriate for lake whitefish in Lake Michigan.