Minimum Sample Size Requirements for Estimating Genetic Diversity in Hatchery Reared Fishes: Muskellunge As a Case Study

Conserving genetic resources within hatchery propagation programs is a focal concern for sustainable fisheries management programs. The Wisconsin Department of Natural Resources muskellunge (Esox masquinongy) propagation program recently implemented comprehensive guidelines to conserve genetic diversity at the hatchery- and stock-level; a critical goal was to minimize genetic changes throughout the propagation process (broodstock to fry to fingerlings). Our objective was to estimate the number of fish of each life stage required to represent the genetic diversity within that life stage (fry, fingerlings). Samples were obtained from Governor Tommy Thompson State Fish Hatchery from all broodstock (N = 47) and 700 fingerlings during 2011, and from all broodstock (N = 72), 500 fry, and 800 fingerlings during 2012. Genetic diversity was assessed at 14 microsatellite loci. We determined that a total of 150 fry gave statistically similar estimates of the number of alleles (A) and observed heterozygosity (H_O) as the total sample of 500 fry. A total of 50-75 fingerlings per rearing pond provided similar estimates of A and H_O as 100 per pond. Reduced sampling effort saves time and money and reduces stress on propagated fishes. This study can serve as a template for conservation genetics sampling within hatcheries.