Transactions of the American Fisheries Society ISSN: 0002-8487 (Print) 1548-8659 (Online) Journal homepage: http://www.tandfonline.com/loi/utaf20 Origin and Straying of Hatchery Winter Steelhead in Oregon Coastal Rivers R. Kirk Schroeder , Robert B. Lindsay & Ken R. Kenaston To cite this article: R. Kirk Schroeder , Robert B. Lindsay & Ken R. Kenaston (2001) Origin and Straying of Hatchery Winter Steelhead in Oregon Coastal Rivers, Transactions of the American Fisheries Society, 130:3, 431-441, DOI: 10.1577/1548-8659(2001)130<0431:OASOHW>2.0.CO;2 To link to this article: http://dx.doi.org/10.1577/1548-8659(2001)130<0431:OASOHW>2.0.CO;2 Published online: 09 Jan 2011. Submit your article to this journal Article views: 136 View related articles Citing articles: 16 View citing articles Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=utaf20 Download by: [Oregon State University] Date: 02 December 2016, At: 13:22 Transactions of the American Fisheries Society 130:431±441, 2001 q Copyright by the American Fisheries Society 2001 Origin and Straying of Hatchery Winter Steelhead in Oregon Coastal Rivers R. KIRK SCHROEDER,* ROBERT B. LINDSAY, AND KEN R. KENASTON Oregon Department of Fish and Wildlife, 28655 Highway 34, Corvallis, Oregon 97333, USA Abstract.ÐWe evaluated the origin and straying of hatchery steelhead Oncorhynchus mykiss among 16 rivers on the Oregon coast to examine rearing or release practices that might contribute to straying. Data were collected on the returning adults of three brood years that had been dif- ferentially marked and released as smolts in 1990±1992. The percentage of strays averaged 11% (range, 4±26%) of the samples of hatchery and wild ®sh in 11 streams where hatchery steelhead were released. Stray hatchery ®sh composed a mean of 22% (range, 9±43%) in 5 streams without hatchery releases. The two predominant factors that contributed to straying were releases of stocks transplanted from their natal basins and releases into adjacent basins. Releases of transplanted stocks into adjacent basins accounted for 41% of the strays, while releases of transplanted stocks into nonadjacent basins accounted for 29% of the strays. Local stocks of steelhead released into adjacent basins accounted for 16% of the strays. The incidence of straying by hatchery ®sh and its widespread occurrence in Oregon coastal rivers present genetic and ecological risks to wild populations of winter steelhead. Strategies to reduce straying may include using local brood stocks, rearing and releasing ®sh within their natal basins, reducing the numbers of hatchery ®sh released, and eliminating some hatchery releases altogether. Homing of adult anadromous salmonids to their the genetic diversity between populations and de- natal stream has been recognized as an important crease the ®tness of wild populations through the adaptation in establishing and maintaining distinct displacement or breakdown of locally adapted gene spawning populations through reproductive iso- complexes (Emlen 1991; Waples 1991a). Gene ¯ow lation (Ricker 1972; Horrall 1981). Mature ®sh increases between nonnative hatchery and wild pop- that migrate to and spawn in a stream other than ulations when hatchery strays successfully spawn the one where they originated are considered strays with wild ®sh, and it can result in the reduced fre- (Quinn 1993). Straying is a natural behavior that quency and subsequent loss of locally adapted alleles enables salmonids to colonize new habitat (Milner (Felsenstein 1997). Hatchery strays spawning in sev- and Bailey 1989), to avoid locally unfavorable eral rivers can also result in a genetically homoge- conditions (Leider 1989), to maintain genetic di- nous population (Adkison 1995; Felsenstein 1997). versity within stocks (Horrall 1981), and to per- A potential ecological effect of stray hatchery ®sh petuate metapopulations (Hanski and Gilpin on wild ®sh is competition in spawning and rearing 1997). The genetically distinct structure of anad- areas (Fresh 1997). In addition, large numbers of romous salmonid populations (e.g., Reisenbichler strays can mask trends in the population abundance et al. 1992) suggests that the successful reproduc- of wild ®sh and bias estimates of the survival and tion of strays naturally occurs at low levels. How- exploitation of wild and hatchery stocks (e.g., La- ever, straying of hatchery ®sh concerns ®sh man- belle 1992). agers because of the potential negative impacts on Concerns about the genetic and ecological im- wild populations of interbreeding between wild pacts of hatchery ®sh on wild ®sh have led to and hatchery ®sh (e.g., Waples 1991a). De®ning proposals for assessing and altering hatchery pro- the ``home'' of hatchery ®sh can be dif®cult be- grams (e.g., NRC 1996) as well as to policy chang- cause local stocks are often reared and released in es in ®sh management agencies. For example, a different locations. In addition, stocks of hatchery wild ®sh management policy adopted in Oregon ®sh are often transplanted to nonnatal streams. sets guidelines for the percentage of hatchery ®sh Stray hatchery ®sh can have genetic and ecolog- allowed in a wild spawning population (ODFW ical effects on wild ®sh populations. Hatchery ®sh 1992). The National Marine Fisheries Service that stray and hybridize with wild ®sh can reduce (NMFS) is also developing guidelines for man- aging stray hatchery ®sh in its efforts to protect * Corresponding author: [email protected] natural populations under the Endangered Species Received April 11, 2000; accepted January 4, 2001 Act (McElhany et al. 2000). Strategies to reduce 431 432 SCHROEDER ET AL. the number of hatchery ®sh in a river basin depend, categories, namely, local stocks and transplanted in part, on knowing the number and origin of the stocks. Local stocks were steelhead released into strays that occur with natural spawners. In addi- their natal basins and included those reared within tion, knowledge of hatchery release practices that the natal basin and those reared outside but re- contribute to straying is important for modifying leased within the natal basin. Transplanted stocks hatchery programs. were steelhead taken from their natal basin and Studies of straying have examined hatchery prac- released into another basin. Some transplanted tices such as release time (Unwin and Quinn 1993; stocks were reared within the basin where they Pascual et al. 1995) and release location (Pascual were released, but most were reared outside the and Quinn 1994; Pascual et al. 1995). A few studies release basin. have examined straying of hatchery salmon Oncor- Release groups returned as adults in the 1991± hynchus spp. over large geographic areas (Labelle 1992 through the 1993±1994 run years. We collected 1992; Unwin and Quinn 1993; Pascual and Quinn data on stray hatchery ®sh in 12 streams by using 1994). Studies of straying in steelhead O. mykiss have trap catches and creel surveys. Seven of these focused on small geographic scales (Shapovalov and streams were stocked with hatchery steelhead (the Taft 1954; Leider 1989) or the effects of smolt trans- Nestucca, Siletz, Yaquina, Alsea, Siuslaw, Coquille, portation in the Columbia River basin (Slatick et al. and Chetco rivers), and ®ve streams received no 1988). We are aware of just one study that examined hatchery ®sh (the Trask, Elk, Sixes, and Winchuck straying of steelhead over a large geographic area rivers, and Drift Creek) (Figure 1). In addition, we (Lirette and Hooton 1988). Our study was initiated used data reported by anglers to examine the per- to examine the origin and straying of hatchery winter centage of stray hatchery ®sh in four streams that steelhead among rivers on the Oregon coast, as well were stocked with hatchery steelhead (the Necani- as to examine the factors in¯uencing patterns of cum, Nehalem, Umpqua, and Rogue rivers). Anglers straying. voluntarily collected scales and reported clip infor- mation under an ODFW program to obtain infor- Methods mation about the catch of steelhead. In this study we considered hatchery steelhead We estimated straying within a surveyed basin as strays if they returned to a river basin other than as the percentage of the total sample of winter the one where they were released. Studies have steelhead (hatchery and wild) that was of stray demonstrated that hatchery steelhead tend to return hatchery origin. We could not calculate a stray rate to speci®c release sites within a river basin (Wag- (i.e., the percentage of a release group that strayed) ner 1969; Slaney et al. 1993). We examined the because we could not account for all adult returns origin of stray steelhead and their spatial distri- of a given release. The hatchery portion of the bution in rivers along the Oregon coast over a return to a basin was divided into a homing com- distance of about 500 km (Figure 1). ponent (those from releases into that basin) and a Hatchery winter steelhead were differentially straying component (those from releases into other marked by excising ®ns or maxillary bones for basins). In catch-and-release ®sheries, we deter- three brood years at seven steelhead hatcheries on mined the catch of wild ®sh from angler interviews the Oregon coast (Figure 1) and were released as during creel surveys. We assigned returning adults smolts in 1990±1992 (Table 1). We generally var- to a release year by using circuli patterns on scales ied the marks within and among release groups to determine age (Chapman 1958). Where no over the 3-year study to reduce bias in estimates scales were available, we used ®sh length to es- of straying attributed to particular groups. Because timate the age of adults. the number of distinct clip combinations is limited Some steelhead had marks that could not be as- and because a few hatcheries that released steel- signed to a particular release and were classed as head into several basins were unable to rear sep- ``unknown'' strays.