Long-term captive breeding does not necessarily prevent reestablishment: lessons learned from Eagle Lake rainbow trout Gerard Carmona-Catot, Peter B. Moyle & Rachel E. Simmons Reviews in Fish Biology and Fisheries ISSN 0960-3166 Rev Fish Biol Fisheries DOI 10.1007/s11160-011-9230- x 1 23 Your article is protected by copyright and all rights are held exclusively by Springer Science+Business Media B.V.. This e-offprint is for personal use only and shall not be self- archived in electronic repositories. If you wish to self-archive your work, please use the accepted author’s version for posting to your own website or your institution’s repository. You may further deposit the accepted author’s version on a funder’s repository at a funder’s request, provided it is not made publicly available until 12 months after publication. 1 23 Author's personal copy Rev Fish Biol Fisheries DOI 10.1007/s11160-011-9230-x RESEARCH PAPER Long-term captive breeding does not necessarily prevent reestablishment: lessons learned from Eagle Lake rainbow trout Gerard Carmona-Catot • Peter B. Moyle • Rachel E. Simmons Received: 7 March 2011 / Accepted: 18 July 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Captive breeding of animals is often cited recovering as habitat. With the exception of an as an important tool in conservation, especially for abundant alien brook trout (Salvelinus fontinalis) fishes, but there are few reports of long-term population in Pine Creek, the habitat factors that led (\50 years) success of captive breeding programs, to the presumed near-extinction of Eagle Lake rainbow even in salmonid fishes. Here we describe the captive trout in the early twentieth century have been amelio- breeding program for Eagle Lake rainbow trout, rated, although the final stages of reestablishment Oncorhynchus mykiss aquilarum, which is endemic (eradication of brook trout, unequivocal demonstration to the Eagle Lake watershed of northeastern Califor- of successful spawning migration) have still not been nia. The population in Eagle Lake has been dependent completed. The Eagle Lake rainbow trout story shows on captive breeding for more than 60 years and that long-term captive breeding of migratory salmonid supports a trophy fishery in the lake. Nevertheless, fishes does not necessarily prevent reestablishment of the basic life history, ecological, and genetic traits of wild populations, provided effort is made to counter the subspecies still seem to be mostly intact. Although the effects of hatchery selection and that natural management has apparently minimized negative habitats are restored for reintroduction. Long-term effects of hatchery rearing, reestablishing a wild success, however, ultimately depends upon eliminat- population would ensure maintenance of its distinctive ing hatchery influences on wild-spawning populations. life history and its value for future use as a hatchery Extinction of Eagle Lake rainbow trout as a wild fish. An important factor that makes reestablishment species becomes increasingly likely if we fail to act possible is that the habitat in Eagle Lake is still intact boldly to protect it and the Eagle Lake watershed. and that Pine Creek, its major spawning stream, is Keywords Salmonidae Á Captive breeding Á G. Carmona-Catot (&) Á P. B. Moyle Hatchery effects Á Species invasions Á Endangered Department of Wildlife, Fish and Conservation Biology, species Á Conservation Á Eagle Lake University of California, Davis, Davis 95616, CA, USA e-mail: [email protected] G. Carmona-Catot Institute of Aquatic Ecology, University of Girona, Introduction 17071 Girona, Catalonia, Spain Captive breeding of animals is often cited as an R. E. Simmons Department of Animal Science, Genomic Variation Lab, important tool in conservation (Soule´ et al. 1986), University of California, Davis, Davis 95616, CA, USA especially for fish (Phillippart 1995). In some cases, it 123 Author's personal copy Rev Fish Biol Fisheries is the final resort for the species, when the last An unusual opportunity to see if a salmonid individuals are taken into captivity, as has happened population long maintained by captive breeding can with California condor (Gymnogyps californianus), revert to a wild, self-sustaining state is found in Eagle black-footed ferret (Mustela nigripes), Arabian oryx Lake rainbow trout (Oncorhynchus mykiss aquilarum). (Oryx leucoryx), European bison (Bison bonasus), and This trout is endemic to a single California watershed Owens pupfish (Cyprinodon radiosus) (Miller and but is now in widespread use in the western USA as a Pister 1971; Kleiman 1989; Snyder and Snyder 2000; hatchery fish. It has been reared in captivity for the first Perzanowski and Olech 2007; Belant et al. 2011). Most year or more of life for more than 60 years and is captive breeding programs, however, are fairly recent stocked annually into its native Eagle Lake, California, in origin and have little long-term experience with to support a trophy fishery (Moyle 2002). The stocked reestablishing wild populations. A general goal of fish, once mature, are captured, spawned, and returned captive breeding is to re-establish species in the wild to Eagle Lake. Some of their progeny are used as brood once suitable habitat is available, although this is not stock for part of the hatchery program. In this respect always possible (Snyder et al. 1996). Major concerns the captive breeding program for Eagle Lake rainbow include loss of fitness for survival in the wild during trout (ELRT) has characteristics of both a supplemen- captivity, through loss of genetic diversity, selection tation hatchery program and a put-and-grow program. for traits that improve survival in captivity but are While the hatchery program probably saved ELRT detrimental in the wild, and loss of learned behaviors from extinction, its principal purpose has been to essential for survival in the wild (Busack and Currens maintain the sport fishery in Eagle Lake and in other 1995; Araki et al. 2007, 2008). water bodies in California. Access of ELRT to their Many hatchery programs for fishes of the family major former spawning tributary (Pine Creek) has been Salmonidae (salmon, trout, charrs, etc.) are arguably completely blocked to allow for easy capture of mature captive breeding on a large scale, although they are fish. Moyle et al. (2008) suggested that the ELRT mostly designed to supplement existing wild popula- should be listed as a threatened species because of its tions or to support fisheries directly (Hilborn 1992; complete dependence on hatchery rearing for survival. Busack and Currens 1995). Fish used for the latter In this paper, we (1) describe the distinctive nature purpose can become completely domesticated (Moyle of Eagle Lake and its watershed, (2) review the 1969; Huntingford 2004); they are raised to be caught biology, history, and recent studies of ELRT, and (3) shortly after release (put-and-take fishery) or are present new information on ELRT life history and released into fairly benign conditions, such as ponds genetics. We then use this information to answer the or reservoirs, with no expectation of natural reproduc- following questions: tion (put-and-grow fishery). Fish from supplementa- • Can a self-sustaining population of ELRT be re- tion hatcheries, however, are expected to survive in the established in its native habitats after nearly wild although mortality rates once released are usually 60 years of captive breeding? extremely high. Nevertheless, supplementation pro- • If so, what changes in management of ELRT are grams have shown considerable success in maintain- required in order to re-establish a self-sustaining ing fisheries but their long-term prospects have been population in the Eagle Lake watershed? questioned (Fraser 2008; Kostow 2008). One reason for concern is loss of fitness for survival in the wild, Finally, we discuss insights gained from this study which in steelhead (Oncorhynchus mykiss) can be in the use of captive breeding for restoration of native significant in 1–2 generations (Araki et al. 2007, 2008, fish. 2009). Fraser (2008) points out that there is little evidence that salmonids with a long hatchery history can establish self-sustaining wild populations. Most of Eagle Lake and its watershed the evidence is equivocal or anecdotal. However, Chilcote et al. (2011) show that wild populations of Eagle Lake (40.6 N, 120.7 W) is the second largest three species of anadromous salmonids have greatly natural lake (24 km long by 3–4 km wide) entirely reduced ability to be self-sustaining when fish of contained in California, with a surface area of hatchery origin are also present. ca. 8,900 ha (Fig. 1). It is situated in northeastern 123 Author's personal copy Rev Fish Biol Fisheries Fig. 1 Eagle Lake basin, showing the location of Pine Creek, the principal spawning tributary of Eagle Lake rainbow trout, and of Bogard Spring Creek, a small tributary at the lower end of the permanent reaches of Pine Creek, that is used for experimental spawning and rearing. Stream sections shown by a dashed line are usually dry in summer. The uppermost ca. 5 km of Pine Creek, which are highly seasonal in flow, are not shown California at an elevation of about 1,555 m (lake Table 1 Species, year and fish stocked in Eagle Lake since surface elevation varies with inflow). This endorheic 1924 (King and Weidlein, unpublished data, 1976; Purdy 1988; (terminal) lake consists of three basins, two of them Pustejovsky 2007) averaging 5–6 m deep, the third averaging 10–20 m Species Year No of fish with a maximum depth of about 23 m. The shallow stocked basins are similar in their limnology and water Coregonus clupeaformis 1879 225,000 temperatures sometimes exceed 21°C in the summer, Ameierus nebulosus 1879 – although the deep basin stratifies, providing a cool Micropterus salmoides 1901–1902/1930 1047 water refuge for trout.