Genetic evaluation of the initiation of a captive population: the general approach and a case study in the endangered pallid sturgeon (Scaphirhynchus albus)

Because of recent environmental changes, a number of species have become critically endangered in the wild. To prevent extinction of these species, captive populations have been established and generally maintained in a manner that attempts to avoid detrimental genetic changes. In particular, wild founders should be unrelated and not inbred. The subsequent generations in captivity should make the effective population size as large as possible to retain the initial genetic variation. Pallid sturgeon (Scaphirhynchus albus) from the upper Missouri River USA have not successfully recruited in decades. Perpetuation of this stock is now accomplished through captive spawning of wild-caught fish with subsequent release of their offspring. In addition to the fish released into the wild, more than 2,000 offspring of the wild fish from 11 year-classes are captively housed. We examined the genetic risks associated with using these fish as a captive population for the future propagation of pallid sturgeon and concluded that the wild individuals are unrelated, non-inbred remnants of a formerly larger population. Further, there is a sufficiently large effective population size (N (e)) present in the captive broodstock for propagation provided that the effective population size can be increased in subsequent generations. This study shows how genetic and evolutionary principles and applications can be used to evaluate the potential founders of a captive population and make recommendations for the long-term evolutionary success of an endangered species.