Mark V. Johnston

Assessment of High Rates of Precocious Male Maturation in a Spring Chinook Salmon Supplementation Hatchery Program

Abstract The Yakima River Spring Chinook Salmon Supplementation Project in Washington State is one of the most ambitious efforts to enhance a natural salmon population currently under way in the United States. Over the past 5 years we have conducted research to characterize the developmental physiology of natural and hatchery-reared wild progeny spring Chinook salmon Oncorhynchus tshawytscha in the Yakima River basin. Fish were sampled at the main hatchery in Cle Elum, at remote acclimation sites, and, during smolt migration, at downstream dams. Throughout these studies, we characterized the maturational state of all fish using combinations of visual and histological analyses of testes, computation of gonadosomatic indices, and measurement of plasma 11-ketotestosterone (11-KT). We established that a plasma 11-KT threshold of 0.8 ng/mL can be used to designate male fish as either immature or precociously maturing approximately 8 months prior to final maturation (1–2 months prior to release as “smolts”). Ou...

Comparison of Life History Traits between First-Generation Hatchery and Wild Upper Yakima River Spring Chinook Salmon

Abstract Life history traits in hatchery and wild spring Chinook salmon Oncorhynchus tshawytscha from the upper Yakima River were compared to determine whether locally adapted traits had diverged after one generation of state-of-the-art artificial propagation. Sex composition in wild- and hatchery-origin fish differed in three of four brood years (P ≤ 0.01). The proportion of hatchery males, primarily age 3, increased from 38% to 49% over time. Conversely, the sex composition of wild fish did not exhibit a similar linear trend. Most hatchery- and wild-origin fish reached maturity at age 4 (≥76%), followed in magnitude by ages 3 and 5. Wild mean age at maturation demonstrated no significant trend over time, while hatchery mean age at maturation declined (P = 0.05). Mean lengths of 3–5-year-old hatchery fish were shorter than those of wild fish of the same age (differences of 2.7 cm for age 3, 1.7 cm for age 4, and 1.9 cm for age 5). Likewise, body weights of hatchery fish were lower than those of wild fish...

Homing and Spawning Site Selection by Supplemented Hatchery- and Natural-Origin Yakima River Spring Chinook Salmon

Abstract It is well known that salmon home to their natal rivers for spawning, but the spatial scale of homing within a river basin is poorly understood and the interaction between natal site fidelity and habitat-based spawning site selection has not been elucidated. Understanding the complex trade-offs among homing to the natal site, spawning site selection, competition for sites, and mate choice is especially important in the context of hatchery supplementation efforts to reestablish self-sustaining natural spawning populations. To address these questions, we examined the homing patterns of supplemented Yakima River spring Chinook salmon Oncorhynchus tshawytscha released from satellite acclimation facilities after common initial rearing at a central facility. Final spawning location depended strongly on where fish were released as smolts within the upper Yakima River basin, but many fish also spawned in the vicinity of the central rearing hatchery, suggesting that some fish imprinted to this site. While...

Effects of Passive Integrated Transponder Tags on Smolt-to-Adult Recruit Survival, Growth, and Behavior of Hatchery Spring Chinook Salmon

Abstract We tagged juvenile upper Yakima River hatchery spring Chinook salmon Oncorhynchus tshawytscha with passive integrated transponder (PIT) and coded wire snout tags in a double-tag study to test the assumptions that tags are not lost and do not affect postrelease survival, behavior, or growth. The average loss of PIT tags was 2.0% (95% confidence interval [CI] = 0.7–3.2%) in juveniles before release and 18.4% in recaptures returning 6 months to 4 years after release (95% CI = 17.2–19.5%). Adult tag losses were not significantly correlated with age of return (analysis of covariance, P = 0.40), indicating that the majority of PIT tag loss had occurred within the first 6 months after release. Smolt-to-adult recruit survival (SARS) of PIT-tagged fish was significantly lower (P < 0.05) than that of non-PIT-tagged (NPT) fish because of tag loss and reduced survival, resulting in an average underestimate of SARS of 25.0%. After correcting for tag loss, we estimated PIT tag-induced mortality to be as great ...

Survival Comparison of Spring Chinook Salmon Reared in a Production Hatchery under Optimum Conventional and Seminatural Conditions

Abstract We found insufficient evidence to conclude that seminatural treatment (SNT; i.e., rearing in camouflage-painted raceways with surface and underwater structures and underwater feeders) of juvenile Chinook salmon Oncorhynchus tshawytscha resulted in higher survival indices than did optimum conventional treatment (OCT; i.e., rearing in concrete raceways with surface feeding) for the specific treatments and environmental conditions tested. We reared spring Chinook salmon from fry to smolt in paired raceways under the SNT and OCT rearing treatments for five consecutive years. For four to nine SNT and OCT raceway pairs annually, we used passive integrated transponder, coded wire, and visual implant elastomer tags to compare survival indices for juvenile fish from release at three different acclimation sites 340-400 km downstream to passage at McNary Dam on the Columbia River, and for adults from release to adult return to Roza Dam in the upper Yakima basin. The observed differences in juvenile and adul...

Comparison of Female Reproductive Traits and Progeny of First-Generation Hatchery and Wild Upper Yakima River Spring Chinook Salmon

Abstract Hatchery and wild female spring Chinook salmon Oncorhynchus tshawytscha from the upper Yakima River were compared to determine whether their reproductive traits had diverged after a single generation of artificial propagation. Fecundity, relative fecundity, individual egg mass, and total gamete mass were all significantly correlated with body length, while reproductive effort (gonadosomatic index) was not. Regressions of trait versus body length often differed significantly among brood years. Hatchery spring Chinook salmon were significantly smaller than wild females over the four brood years examined. After brood year and body length (when necessary) were accounted for, wild females had an average of 8.8% more total gamete mass, 0.8% more individual egg mass, 7.7% greater fecundity, and 0.8% greater reproductive effort than hatchery females. Relative fecundity (the number of eggs per centimeter of body length) was on average 1.3% greater in hatchery females. We also compared body size at yolk ab...

A Synthesis of Findings from an Integrated Hatchery Program after Three Generations of Spawning in the Natural Environment

AbstractThe 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 findin...