Mark Recapture Reveals Variance in Broodstock Reproductive Success in a Sturgeon Conservation Aquaculture Program

Conservation aquaculture programs (CAPs) are managed to maximize a supplemented population’s adaptive potential. Although hatchery practices to maximize N_e and minimize relatedness may create diverse, non-inbred cohorts for stocking, post-release selection pressures may reduce broodstock contributions and increase relatedness at recruitment.  We used a mark recapture database and parentage analysis to assess variability in post-stocking apparent survival in the Kootenai River white sturgeon CAP.  Using individuals assigned to family using PIT tags or genetic analysis, we determined the number of families from the 2002, 2004-2011 year classes currently at large in the Kootenai River.  First year analyses detected only 26% of CAP families through recapture of one or more progeny.  Within year classes, the mean number of progeny detected per family ranged from 0.12 (2010) to 8.33 (2002).  Re-calculating neutral genetic diversity levels preserved by the CAP using only broodstock with surviving offspring showed that significantly less genetic diversity was represented within years (excluding 2002) but similar levels were preserved across years when compared to previous projections that assumed contributions from all broodstock. However, large variance in reproductive success among broodstock may reduce the N_e of released cohorts, reducing the N_e of the wild population and increasing relatedness among future spawners. Future years of this study will increase the number of recaptures and incorporate additional data to identify variables associated with family success.