Status of Biodiversity of Taxa and Nontaxa of Salmonid Fishes: Contemporary Problems of Classification and Conservation

Abstract

The recent publication by Nehlsen et al. (1991) makes it clear that the greatest challenge in preserving the genetic diversity of salmonid fishes concerns the protection of nontaxa. These authors list 214 “stocks” of Pacific salmon and steelhead at risk of extinction in California, Oregon, Washington, and Idaho. Of these, 101 are judged to be at high risk and 18 may already be extinct. These stocks of salmon and trout do not meet any of the generally accepted criteria for taxa recognition. They are not geographically isolated and although they maintain their integrity by reproductive isolation as a result of homing, they exhibit virtually no distinguishing morphological nor quantifiable genetic characteristics. Their intraspecific differentiation concerns life history and ecological adaptations to specific environments. Intraspecific fracturing of a species into numerous discrete stocks or populations is driven by natural selection to expand future evolutionary options for genetic continuity and acts to maximize the abundance of a species. Obviously, any conservation program to preserve biodiversity, to be truly effective, must begin at the lowest nontaxon level.