This study investigated whether culturing age-0 steelhead (Oncorhynchus mykiss) in habitat-enriched rearing tanks, containing a combination of in-water structure, underwater feeders, and overhead cover, affected competitive ability and habitat use compared with juveniles cultured in more conventional vessels. In laboratory tests, steelhead juveniles grown in the enriched tanks socially dominated size-matched competitors grown in conventional tanks. When both treatments were introduced into separate sections of a quasi-natural stream, no differences in growth were found between them. However, when intermixed, fish reared in the enriched tanks grew at a higher rate than conventionally reared competitors, suggesting greater competitive ability of juveniles grown in the enriched tanks. Visual isolation and defensible food resources in combination in the enriched tanks were considered as the primary factors causing the observed competitive asymmetries. Steelhead juveniles from the two rearing environments exhibited very similar use of woody structure in the quasi-natural stream, both in the presence and in the absence of mutual competition. Rearing steelhead in more naturalistic environments could result in hatchery fish that behave and integrate into the postrelease (natural) environment in a manner more similar to wild fish.

The use of captive broodstocks is becoming more frequently employed as the number of species facing endangerment or extinction throughout the world increases. Efforts to rebuild the endangered Snake River sockeye salmon, Oncorhynchus nerka, population have been ongoing for over a decade, but the use of microsatellite data to develop inbreeding avoidance matrices is a more recent component to the program. This study used known genealogical relationships among sockeye salmon offspring to test four different pairwise relatedness estimators and a maximum-likelihood (M-L) relatedness estimator. The goal of this study was to develop a breeding strategy with these estimators that would minimize the loss of genetic diversity, minimize inbreeding, and determine how returning anadromous adults are incorporated into the broodstock along with full-term hatchery adults. Results of this study indicated that both the M xy and R QG estimators had the lowest Type II error rates and the M-L and R R estimators had the lowest Type I error rates. An approach that utilizes a combination of estimators may provide the most valuable information for managers. We recommend that the M-L and R R methods be used to rank the genetic importance of returning adults and the M xy or R QG estimators be used to determine which fish to pair for spawning. This approach provides for the best genetic management of this captive, endangered population and should be generally applicable to the genetic management of other endangered stocks with no pedigree.

We investigated competition among newly emerged fry from captive-reared and wild female coho salmon Oncorhynchus kisutch by conducting dominance challenges and growth and survival experiments in laboratory stream channels. Newly emerged fry from captive-reared females won a significant majority (72.7%) of dyadic dominance challenges against fry from wild females. In a growth and survival experiment conducted from emergence to 30 d postemergence, fewer captive brood fry died of apparent starvation when food was limited than wild fry, further suggesting a competitive advantage for the captive brood fry. All fry used in the study were paternal half-sibs, so observed differences between captive brood and wild fry were attributed to the maternal parent. We hypothesize that fry coloration resulting from differences in egg color between wild and captive-reared females may have influenced the observed competitive asymmetries. If so, such differences might be ameliorated by changes in husbandry practices such as providing more natural diets.

The use of diets supplemented with live food lo increase the postrelease foraging ability of hatchery-reared fall chinook salmon Oncorhynchus tshawytscha was investigated. Replicate groups of fry were reared in six 2.4-m-diarneter circular tanks and fed one of two diets. Fish in three tanks received a commercially available pelletized diet; fish in the other three tanks were given the opportunity to forage on natural live prey (mysids, mosquito larvae, chironomid larvae, and daphnia) prior lo their daily ration of pellets. Foraging by individual lish was observed in special 200-L tanks, and fish conditioned to live food fed on twice as many familiar prey (chironomids) and novel prey (mayfly larvae) as unconditioned fish fed on. This suggests that diets supplemented with live food can be used to increase the postrelease foraging effectiveness of hatchery-reared chinook salmon.

In November 1991, the U.S. National Marine Fisheries Service listed Snake River Sockeye Salmon (Oncorhynchus nerka) as endangered under the U.S. Endangered Species Act (ESA). The last known remnants of the Snake River stock return to Redfish Lake in the Sawtooth Valley in central Idaho. In the ensuing two decades since the ESA listing, many actions have been taken to conserve the population, including the initiation of a hatchery‐based gene rescue program. The chief aim of this article is to describe the development and implementation of hatchery‐based gene rescue activities, review present‐day release strategies and associated adult returns, and describe a new effort underway to expand program production to more effectively address recolonization and local adaptation objectives. In addition, we describe achievable population triggers to allow the transition from a hatchery‐based effort to a habitat‐based effort that should allow natural population recovery to proceed.

The U.S. Pacific Northwest (PNW) has one of the largest suites of hatchery programs for anadromous salmonids in the world, with about 500 programs producing about 325 million juvenile fish. A total of about 0.7 million Pink Salmon Oncorhynchus gorbuscha, 21 million steelhead O. mykiss, 50 million Chum Salmon O. keta, 32 million Sockeye Salmon O. nerka, 41 million Coho Salmon O. kisutch, and 182 million Chinook Salmon O. tshawytscha are released annually from PNW hatcheries. These fish provide for robust, sustainable fisheries, and their production and release are designed to meet legal agreements, international treaties, and treaty trust responsibilities. However, this level of hatchery production is often assumed to have negative effects on the conservation of U.S. Endangered Species Act–listed salmon populations in the region. A review of the development of best management practices to balance the conservation and sustainable fisheries goals for PNW salmon hatcheries indicates that to be successful every hatchery program must (1) be scientifically defensible and relate to both published standards and statistically relevant outcomes, (2) have well‐defined and documented goals with explicit biological and operational specifications, and (3) have protocols in place that enable managers to respond adaptively to new information. The focus should be on the biological integrity of the populations being propagated in or influenced by the hatchery environment, as opposed to the management of the physical facilities. Complete documentation for a proposed hatchery action component should include items ranging from hatchery location and water source(s) to all aspects of animal husbandry and harvest and the management plans for adult returns. The current science for items should be described and the choice of an action component justified in terms of either the scientific or policy basis of the expect outcome. Where appropriate, complete monitoring and evaluation plans for the proposed actions need to be described.

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Innate predator recognition and fright response behaviours were compared in a laboratory study between second generation offspring from two related populations of steelhead trout Oncorhynchus mykiss from Sashin Creek, Alaska. The stream population was anadromous and co-occurred with Dolly Varden Salvelinus malma, a piscivore and salmonid predator. Sashin Lake, formerly fishless, was stocked with fish from the stream population in 1926 and that population has been isolated from heterospecific piscine predation ever since. Fish from the lake population were predicted to show diminished innate fright response to Dolly Varden scent relative to the stream population. The behaviour of 60 individual juvenile O. mykiss from each population was measured and observed in aquaria before and after exposure to chemical cues of Dolly Varden, conspecific skin extract, or a control of distilled water. The alarm substances caused significant behavioural changes in both populations in the amount of time spent motionless, time spent in the lower water column and feeding frequency. No significant differences were observed between the stream and lake populations in the change in behaviour between pre-and post-stimulus observation periods for any of the measured fright responses, indicating that the sequestered lake population has not lost the ability to detect or respond to conspecific alarm substances or Dolly Varden scent.