netic pool of a species and will jeopardize the recovery of the species forever. The present large-scale collapse of coho salmon and the fragmentation of this species range clearly demonstrates that conservation biology must take precedence immediately if we are to save this and other collapsing salmonid populations.
It is exactly the progressive decline, attrition, and lack of genetic diversity in all of our coho salmon populations over their entire range that threaten the future of this species. The loss of single population hinders the entire species ability to survive environmental change, and reduces the ability to evolve and persist into the future.
Artificial Propagation and Loss of Between-Population Diversity
Hatchery-origin fish have not been used to successfully re-build or re-establish coho salmon populations in the region. In general, there are very few (if any) examples of hatchery programs that led to successful re-building of wild populations of Pacific salmon within their native range ( Miller et al. 1990). Despite this history, some hatchery proponents continue to make optimistic projections of the future benefits of fish culture, with little or no scientific evidence to back up their claims. When successful in terms of producing hatchery fish, artificial propagation breeding tends to reduce, rather than increase, diversity of wild populations.
The potential and demonstrated adverse genetic effects of artificial propagation of salmonid populations have been discussed in several recent reviews (Hindar et al. 1991, Waples 1991). The capture of brood stock itself can be destructive of small or declining wild populations. Due to small broodstock populations, pre-spawning mortality during capture or transport, unnatural mating combinations, differential viability of gametes in artificial situations, disease, and artificial selection, wild brood stock typically contribute little genetic diversity to subsequent generations of hatchery fish (Bartley et al. 1992). The taking of larger numbers of wild fish for broodstock in an attempt to overcome these problems in hatchery stocks merely increases the risks for wild populations.
Large or repeated introductions of hatchery fish (foreign stock, hybrid stock, or local-origin stock altered by artificial selection) pose additional risks for wild fish (Steward and Bjornn 1990, Waples 1991, Hindar et al. 1991). Introduction of hatchery fish can adversely affect wild fish through competition and other processes. Maladaptive phenotypes can be introduced (Nickelson et al. 1986) and may temporarily persist in the population, particularly where wild population densities are low or habit has been altered (Campton 1987).
The failure of hatchery programs to boost or re-establish wild populations of coho salmon has been repeatedly demonstrated. Nickelson et al. (1986) documented the net negative effects of stocking coho pre-smolts in coastal Oregon streams, a practice still widespread in Washington and California. The effects of hatchbox programs and fry releases, widespread in all three states, have never been adequately evaluated. Hallock and Fry (1967) reported that numerous introductions of coho salmon had failed to re-establish a self-sustaining run in the Sacramento River. Hope (1993) documented in detail the many failed efforts to restore northern California coastal coho with artificial propagation, starting in the 1940s and continuing through the present. Many if not most coho streams in the region have a similar, long history of introductions of hatchery-origin coho salmon. In many cases no fish return; in others first-generation returns are followed by failure of the second generation to reproduce successfully. Little monitoring of these programs occurs.
The litany of repeated failure in attempts to rebuild or re-establish self-sustaining wild populations with diverse kinds of artificial propagation argues that conservation of wild, indigenous populations of coho salmon in their native habitat is the only prudent and defensible course of action. The many potential side 