Genetic Effects of Hatchery Propagation and Rearing in the Endangered Rio Grande Silvery Minnow, Hybognathus amarus

Abstract

The Rio Grande silvery minnow, Hybognathus amarus, is a federally endangered cyprinid now confined to the middle Rio Grande, New Mexico, in a fraction of its former range. The precipitous decline of the remaining wild population and lack of recruitment in the summer of 2000 prompted collection and placement of eggs and wild fish in propagation facilities. The aim of this study was to assess the genetic effects of hatchery propagation in the Rio Grande silvery minnow using 10 microsatellite loci and partial mitochondrial ND4 sequences. Three hatchery stocks (2001, 2002, and 2003) and the wild source population (collected in 2001–2002) were considered. Principal findings were; (i) captively spawned and reared Rio Grande silvery minnow had depleted levels of allelic diversity but similar levels of heterozygosity to the wild population, and (ii) fish raised from wild-caught eggs maintained similar levels of allelic diversity but had higher inbreeding coefficients than the wild source stock. With the repatriation of over 500,000 Rio Grande silvery minnow to the Rio Grande, the genetic effects of propagation are likely to impact the remaining wild population, especially as numbers in the wild continue to decline.