Assessing the genetic risks of a conservation hatchery program.

While artificial propagation can serve as a conservation tool that provides demographic support, it can also incur domestication and outbreeding depression that risks unintended fitness consequences to both target and connected populations. When artificial propagation programs are temporarily implemented, the interaction between program duration and species life history might determine the potential for such fitness consequences. Here, we develop a mathematical model to quantify approaches to mitigate unintended fitness consequences in temporary artificial propagation programs. We build and parameterize our model on a conservation aquaculture-based recovery program for white sturgeon (Acipenser transmontatus) in the Nechako River (British Columbia), which might impose genetic risks on the adjacent populations within the Fraser River. We find that within time scales of 50-200 years the life history characteristics of white sturgeon, particularly late age of maturity and longevity, typically reduce the genetic risks associated with captive breeding, compared to shorter-lived species like salmonids. Genetic effects of gene flow from hatchery-origin individuals to nearby wild populations accumulate at a rate inversely proportional to the generation time of the population, and thus slowly in long-lived species. The slow time scale of white sturgeon population dynamics also reduces the importance of non-linear feedbacks, which can amplify the genetic and demographic effects of artificial propagation on wild populations over the long term. The slow rate at which risks accumulate in this system provides a window of opportunity to learn and adapt management while the risks of hatchery inputs remain relatively small.