Assessment of Genetic Diversity for American Shad in the Santee–Cooper River Basin of South Carolina prior to Hatchery Augmentation

Abstract

AbstractAmerican shad Alosa sapidissima once supported large commercial fisheries along the Atlantic coast, but by the early 1980s many of these fisheries had declined precipitously. In contrast to most Atlantic coastal rivers, the abundance of American shad in the Santee–Cooper River basin of South Carolina has grown substantially; still, much of their upstream spawning habitat in this watershed has been restricted or adversely affected by impoundments. In an effort to rebuild populations in upstream river reaches of the Santee–Cooper basin, state and federal agencies developed an approach relying on hatchery augmentation, the relocation of prespawning adults, and the construction of permanent fish passage structures. Genetic monitoring was adopted to ensure that the genetic integrity of the population remains intact during the rebuilding process. Our study provided an initial assessment of genetic diversity for the genetic monitoring program. There were three components to the study: an assessment of within‐basin genetic stock structure, a comparison of genetic diversity (the number of alleles and observed heterozygosity) between hatchery and wild stocks, and an evaluation of molecular tags for monitoring hatchery returns. The estimation of genetic diversity and the assessment of molecular tags were based on 10 microsatellite loci. We found no apparent stock structure in the Santee–Cooper basin and no difference in genetic diversity between broodstock and their wild counterparts. Eight microsatellite markers provided enough resolution to successfully (>95% assignment success) match returning American shad with their respective hatchery parents. Our results highlight the utility and importance of integrating genetic information in supportive breeding programs in an effort to evaluate the programs’ effectiveness (both in terms of increasing the census size and in terms of maintaining the long‐term viability of a population).Received March 18, 2011; accepted August 8, 2011