The Cle Elum Supplementation and Research Facility in the Yakima River basin, Washington, is an integrated spring Chinook Salmon Oncorhynchus tshawytscha hatchery program designed to test whether artificial propagation can increase natural production and harvest opportunities while keeping ecological and genetic impacts within acceptable limits. Only natural‐origin (naturally spawned) fish are used for hatchery broodstock. Spawning, incubation, and early rearing occur at a central facility; presmolts are transferred for final rearing, acclimation, and volitional release at sites adjacent to natural spawning areas, where returning adults can spawn with natural‐origin fish. The first wild broodstock were collected in 1997, and age‐4 adults have returned to the Yakima River since 2001. An unsupplemented population in the adjacent Naches River watershed provides a reference for evaluating environmental influences. The program has been comprehensively monitored from its inception. A synthesis of findings, many already published, is as follows: supplementation increased the harvest, redd counts, and spatial distribution of spawners; natural‐origin returns were maintained; straying to nontarget systems was negligible; natural‐origin females had slightly higher breeding success (production of surviving fry) in an artificial spawning channel, while the behavior and breeding success of natural‐ and hatchery‐origin males were similar; hatchery‐origin fish showed differences in morphometric and life history traits; high rates of hatchery age‐2 (minijack) production were reported, but the observed proportions of out‐migrating juvenile and adult (ages 4 and 5) returning males were comparable for hatchery‐ and natural‐origin fish; hatchery smolts did not affect the levels of pathogens in natural smolts; and the ecological interactions attributed to the program were within adopted guidelines. Continued study is required to assess the long‐term impacts on natural production and productivity.

Precocious maturation of artificially propagated male Chinook salmon Oncorhynchus tshawytscha has the potential to alter abundance and distribution of males in freshwater and thereby influence ecological and genetic interactions with other fish in the natural environment. Between 1999 and 2007, the Cle Elum Supplementation and Research Facility has produced and released into the upper Yakima River basin of Washington an annual average of 124,573 males that mature precociously. We investigated the abundance and distribution of precociously mature male spring Chinook salmon of hatchery and natural (wild) origin during the spawning season (4–7 months after hatchery release) in the Yakima River. We counted the number of precocious males on the spawning grounds while snorkeling during the peak of spawning and electrofished to determine abundance and distribution of precocious males away from redds. We also collected Chinook salmon to determine percent precocity and size and age distributions. The number of precocious hatchery males on redds was less than 0.05% of the total number of fish released, and they were significantly less abundant on redds than precocious wild males. Between 1999 and 2007, the mean annual abundance of precocious age‐1 hatchery males observed on the spawning grounds was 22 fish (range, 0–78). Precocious hatchery and wild males were both found throughout the spawning range during the spawning season, but significant differences in distribution between origins were detected. Precocious hatchery males were proportionately more abundant in the most downstream sampling reach and less abundant in a tributary with no hatchery facilities. In addition, most precocious hatchery males were found downstream of spawning areas during the spawning season. It appears that many precocious hatchery males migrate downstream from release and fail to migrate back to the spawning grounds, or they die within the Yakima River before spawning. Thus, precocious male Chinook salmon resulting from hatchery production in the Yakima River do not contribute favorably to harvest and may pose ecological risks to other taxa, but most of these fish have a low probability of contributing genes to future generations.

Pacific trout Oncorhynchus spp. in western North America are strongly valued in ecological, socioeconomic, and cultural views, and have been the subject of substantial research and conservation efforts. Despite this, the understanding of their evolutionary histories, overall diversity, and challenges to their conservation is incomplete. We review the state of knowledge on these important issues, focusing on Pacific trout in the genus Oncorhynchus. Although most research on salmonid fishes emphasizes Pacific salmon, we focus on Pacific trout because they share a common evolutionary history, and many taxa in western North America have not been formally described, particularly in the southern extent of their ranges. Research in recent decades has led to the revision of many hypotheses concerning the origin and diversification of Pacific trout throughout their range. Although there has been significant success at addressing past threats to Pacific trout, contemporary and future threats represented by nonnative species, land and water use activities, and climate change pose challenges and uncertainties. Ultimately, conservation of Pacific trout depends on how well these issues are understood and addressed, and on solutions that allow these species to coexist with a growing scope of human influences. Conservación de la diversidad de truchas nativas del Pacífico en el oeste de NorteaméricaLa trucha del Pacífico Oncorhynchus spp. en el oeste de Norteamérica tiene un alto valor desde el punto de vista ecológi-co, socioeconómico y cultural, y ha sido objeto de importantes esfuerzos de conservación e investigación. A pesar de ello, el conocimiento que se tiene sobre su historia evolutiva, diversidad general y retos de conservación sigue siendo incompleto. Se hace una revisión del estado del conocimiento sobre estos puntos, con énfasis en la trucha del Pacífico dentro del género Oncorhynchus. Si bien la mayor parte de los estudios hechos sobre salmónidos se enfocan al salmón del Pací-fico, aquí nos enfocamos en la trucha del Pacífico ya que ambos groupos de especies comparten una historia evolutiva en común sobre todo en lo que se refiere al extremo sur de sus rangos de distribución. En investigaciones llevadas a cabo en décadas recientes, se han revisado varias hipótesis relativas al origen y diversificación de la trucha del Pacífico a lo largo de su rango de distribución. Aunque se han logrado identificar adecuadamente las amenazas pasadas que enfrentó la trucha del Pacífico, las amenazas actuales y futuras que representan especies no nativas, actividades de uso de tierra y agua y el cambio climático se consideran importantes retos e incertidumbres. Al final, la conservación de la trucha del Pacífico depende de qué tan bien se comprendan y abordan estos temas, y de las soluciones que les permitan a estas especies coexistir con una gama creciente de influencias humanas. Conservation de la diversité de la truite du Pacifique indigène dans l'ouest de l'Amérique du NordLes truites du Pacifique ou Oncorhynchus spp. dans l'ouest...

We evaluated the changes in (1) the abundance, size, and biomass of rainbow trout Oncorhynchus mykiss, (2) the abundance of spring Chinook salmon O. tshawytscha parr, and (3) the combined biomass of rainbow trout and Chinook salmon parr after nine annual releases of approximately 250,000 Chinook salmon and coho salmon O. kisutch smolts into the North Fork of the Teanaway River, Washington. The trout and salmon were sampled in two treatment locations consisting of five sites and three control locations consisting of seven sites before (1990–1998) and during hatchery releases (1999–2007). We detected statistically significant decreases of rainbow trout abundance and biomass in both treatment streams relative to two of the three control streams. Furthermore, all of the differences in abundance between treatment and control streams were in the negative direction. All but one of the differences in biomass was negative. The only statistically significant change in the combined biomass of spring Chinook salmon parr and rainbow trout before and during supplementation was negative, and five of the six differences in combined biomass were negative. Only one of the four comparisons of the ratio of the log‐transformed weight to length of rainbow trout was statistically significant, and it decreased during supplementation; one‐half of the comparisons were positive and the other half negative. The changes to rainbow trout abundance and biomass were probably the result of the cumulative impacts from hatchery‐released Chinook salmon smolts and an increase in naturally produced Chinook salmon parr.

We compared the backpack electrofishing capture efficiencies and Petersen-type mark-recapture abundance estimates of resident rainbow trout Oncorhynchus mykiss that had recovered for 24 h versus 3 h after electrofishing, handling, marking, and release in thirteen 100-m sites in four Yakima River basin tributary streams in central Washington State. Our results indicate that the catchability of rainbow trout was not significantly different between the two recovery periods (P ¼ 0.27). Similarly, Petersen-type mark-recapture abundance estimates did not differ between the two recovery periods (P ¼ 0.20). Despite vigilant effort at installing and maintaining block nets during the 24-h period, we detected fish movement out of 75% of our sites. In addition, our block nets collapsed or were destroyed by small animals in 36% of sites used for a 24-h recovery period; therefore, valid estimates could not be calculated. In contrast, no movement or net failure was detected during the 3-h recovery period. Some of the advantages of a 3-h recovery period between mark-recapture backpack electrofishing events include (1) increased probability of generating a population estimate because of a low threat of block-net failure; (2) lower probability of violating the movement assumption associated with the Petersen-type mark-recapture estimator; and (3) completion of field sampling within a single site visit on a single day. We believe that these advantages should be considered when designing sampling protocols for enumerating stream fish populations.