Conservation of Wild Fish Populations: Preserving Genetic Quality Versus Genetic Diversity

Fish provide about twenty percent of the global demand for animal protein consumption, yet nearly forty percent of commercial fisheries have now collapsed or are in serious decline. In response to this collapse, governments have invested millions of dollars into artificial breeding programs, but many have failed to rehabilitate dwindling wild stocks. This failure may lie in the lack of knowledge about the genetic architecture of fitness – the genes and genotypes that are associated with individual survivorship and performance in natural environments. In this paper we present data from our work on Chinook salmon, as well as draw on data from the literature, to discuss (1) the genetic architecture of fitness, (2) the importance of additive and non-additive genetic effects on fitness, and (3) natural breeding and the preservation of genetic adaptations. We argue that most artificial breeding programs do not maintain genetic adaptations and consequently are ineffective at rehabilitating or enhancing wild populations. Moreover, there is no evidence that preserving genetic diversity as measured from neutral genetic markers increases fish performance or population viability outside of populations that experience strong inbreeding depression, or that genetic diversity increases the potential for populations to adapt to changing environments. We suggest that artificial breeding programs should be used only as a last resort in cases where populations face imminent extirpation and that such programs must shift the focus from preserving genetic diversity to preserving genetic adaptations. We discuss the potential role of including aspects of natural breeding in artificial breeding programs to meet this goal.