Long-term captive breeding does not necessarily prevent reestablishment: lessons learned from Eagle Lake rainbow trout

Abstract

Captive breeding of animals is often cited as an important tool in conservation, especially for fishes, but there are few reports of long-term (\50 years) success of captive breeding programs, even in salmonid fishes. Here we describe the captive breeding program for Eagle Lake rainbow trout, Oncorhynchus mykiss aquilarum, which is endemic to the Eagle Lake watershed of northeastern California. The population in Eagle Lake has been dependent on captive breeding for more than 60 years and supports a trophy fishery in the lake. Nevertheless, the basic life history, ecological, and genetic traits of the subspecies still seem to be mostly intact. Although management has apparently minimized negative effects of hatchery rearing, reestablishing a wild population would ensure maintenance of its distinctive life history and its value for future use as a hatchery fish. An important factor that makes reestablishment possible is that the habitat in Eagle Lake is still intact and that Pine Creek, its major spawning stream, is recovering as habitat. With the exception of an abundant alien brook trout (Salvelinus fontinalis) population in Pine Creek, the habitat factors that led to the presumed near-extinction of Eagle Lake rainbow trout in the early twentieth century have been ameliorated, although the final stages of reestablishment (eradication of brook trout, unequivocal demonstration of successful spawning migration) have still not been completed. The Eagle Lake rainbow trout story shows that long-term captive breeding of migratory salmonid fishes does not necessarily prevent reestablishment of wild populations, provided effort is made to counter the effects of hatchery selection and that natural habitats are restored for reintroduction. Long-term success, however, ultimately depends upon eliminating hatchery influences on wild-spawning populations. Extinction of Eagle Lake rainbow trout as a wild species becomes increasingly likely if we fail to act boldly to protect it and the Eagle Lake watershed.

Postrelease exploration and diel activity of hatchery, wild, and hybrid strain brown trout in seminatural streams

“…Stocking has prevented extinction in some populations (e.g. Carmona-Catot et al 2012) and many fisheries would likely collapse without stock enhancement programs (Cowx et al 2012). Despite of the high stocking efforts stock assessments report decreases of recapture rate over time (e.g.…”

Survival and Reproduction of Myxobolus cerebralis-Resistant Rainbow Trout Introduced to the Colorado River and Increased Resistance of Age-0 Progeny

“…Extirpations of wild salmonid populations have been caused by a variety of factors and have led to a focus on captive breeding (i.e., hatcheries) to sustain or reintroduce populations [1] – [4] . However, successful reintroduction attempts using captive-reared salmonids usually involve mitigating or removing the factors responsible for the original extirpation [5] .…”

Survival and Traits of Reconditioned Kelt Steelhead Oncorhynchus mykiss in the Yakima River, Washington

“…Causes for these declines include a host of environmental and human-induced factors (Raymond 1988;NRC 1996;Williams et al 1999). Common tools for increasing abundance of imperiled species in the wild include nature reserves (Margules and Pressey 2000), restoration ecology (Dobson et al 1997), artificial propagation and release of progeny from wild parents (Cuenco et al 1993), captive rearing (Berejikian et al 2001;Carmona-Catot et al 2012), and use of cryopreserved wild gametes to produce offspring artificially (Cloud et al 1990). Historically, there have been no artificial breeding programs for Yakima River steelhead, and annual adult returns to the Yakima River average 98% wild, the rest being some hatchery strays from other CRB tributaries (Yakama Nation unpublished data).…”