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Objective: The potential influence (i.e., impact rate) of catch‐and‐release fisheries on wild steelhead Oncorhynchus mykiss is poorly understood and is a function of the abundance of wild fish, how many fish are encountered by anglers (i.e., encounter rate), and the mortality of fish that are caught and released. In Idaho, estimates of wild steelhead encounter rates have been derived using the number of wild and hatchery steelhead passing Lower Granite Dam, the number of hatchery steelhead harvested, and the number of hatchery steelhead caught and released. The method includes assumptions that hatchery and wild steelhead have equal encounter rates and catch‐and‐release mortality is 5% for wild steelhead. Here, we investigated wild and hatchery steelhead encounter rates by anglers, estimated catch‐and‐release mortality, and concatenated both aspects to examine how existing recreational steelhead fisheries influence wild steelhead mortality. Methods: We sampled, tagged, and released 1,251 spawn‐year 2020 (SY2020) and 1,956 spawn‐year 2021 (SY2021) adult steelhead at Lower Granite Dam with T‐bar anchor tags and passive integrated transponder (PIT) tags to estimate steelhead encounter rates and catch‐and‐release mortality. Differences in survival of caught steelhead and those not reported as caught were evaluated using detections at various locations (e.g., PIT arrays, weirs). Result: Estimated encounter rates were 43.7% (95% credible interval; 28.2%, 100.0%) for wild fish and 46.7% (29.6%, 100.0%) for adipose‐clipped fish in SY2020. In SY2021, encounter rates were 47.2% (32.4%, 100.0%) for wild fish and 52.3% (37.1%, 100.0%) for adipose‐clipped fish. Based on detections of caught fish and those not reported as caught, catch‐and‐release mortality of wild steelhead was estimated to be 1.6% (0.0%, 5.2%). Wild steelhead impact rates were 0.7% (0.0%, 2.7%) in SY2020 and 0.7% (0.0%, 2.8%) in SY2021. Conclusion: Estimated rates of impact on wild steelhead were consistent and low across years despite major differences in the structure of the fisheries. Our results suggest assuming that encounter rates are equal between hatchery and wild steelhead, and that steelhead catch‐and‐release mortality is 5%, will likely lead to a conservative estimate of the wild steelhead impact occurring from catch‐and‐release fisheries. Impact statementWith wild steelhead numbers declining in many parts of North America, a dilemma between providing angling opportunity and wild steelhead conservation can develop. We show that encounter rate plays a larger role than mortality regarding catch‐and‐release angling on overall impact rates. Our method provides a direct, reliable estimate of encounter rates across multiple scales. [ABSTRACT FROM AUTHOR]

Management of hatchery and wild stocks of steelhead Oncorhynchus mykiss within the same watershed requires careful consideration when management objectives include the use of the hatchery stock to meet fishery objectives while maintaining the genetic integrity of coexisting wild stocks. This scenario can be further complicated when management objectives for the hatchery stock include supplementation of natural production. The lower Clearwater River in Idaho provided an ideal location to evaluate hatchery steelhead genetic influence within a drainage with separate wild steelhead and supplementation management emphasis areas. We collected 813 genetic samples from wild juvenile steelhead from two sample years in 10 tributaries to the lower Clearwater River to explore genetic structure and assess hatchery influence. Overall, levels of genetic diversity of wild groups were comparable with those observed elsewhere in the Snake River basin. Estimates of effective population size of sample tributaries ranged from 22 to 198 spawners, with a median of 84. All but two tributaries had >50 spawners, and evidence of natural gene flow from other stocks was observed. Results of the study display three zones of hatchery influence in the lower Clearwater River: (1) no influence in lower tributaries with wild steelhead emphasis, (2) moderate influence in wild steelhead tributaries in close proximity to the hatchery facility, and (3) significant influence in hatchery‐supplementation tributaries. Interestingly, a number of wild steelhead reporting groups from elsewhere in the Snake River basin were observed in the assignments of study fish, suggesting movement of wild steelhead among larger drainage areas. Techniques outlined in this study can be used to monitor future hatchery influence in the Clearwater River drainage, track historic versus contemporary genetic influence in the drainage, and apply to other watersheds with hatchery and wild steelhead management objectives. [ABSTRACT FROM AUTHOR]

Mountain Whitefish Prosopium williamsoni have failed to garner the same level of attention as other members of the salmonid family in terms of scientific investigations, especially with regard to habitat associations and population status. Consequently, we used snorkel survey data from 1985 to 2019 to relate a suite of environmental factors to Mountain Whitefish occupancy and abundance and to estimate population growth rates in central Idaho. Mountain Whitefish population growth rates in the majority of subbasins in central Idaho appear to be stable or increasing over the past several decades, but more so in the Salmon River basin than in the Clearwater River basin. Mountain Whitefish occupancy and abundance were higher in stream reaches that were lower in elevation and gradient and larger in size, with an occupancy rate of <0.10 in stream reaches that were <6 m average wetted width but >0.50 in stream reaches that were ≥9 m average wetted width. Road density was positively associated with the occupancy and abundance of Mountain Whitefish, contrasting previous studies that generally report negative associations between road density and salmonid population metrics. While this relationship may simply be correlative in nature, in the relatively sterile lotic environment of central Idaho, such anthropogenic disturbance may inadvertently result in nutrient enrichment, potentially benefitting the forage base of Mountain Whitefish. We also observed that conductivity positively influenced Mountain Whitefish abundance, likely stemming from its direct effect on stream productivity. Although the status of Mountain Whitefish in central Idaho appears generally stable, the paucity of studies reporting on the status of this species highlights the need for additional research devoted to a better understanding of trends in Mountain Whitefish abundance across their range. [ABSTRACT FROM AUTHOR]

Managing fisheries for species of conservation concern, such as steelhead Oncorhynchus mykiss fisheries in Idaho where wild steelhead are incidentally caught and released, requires a tradeoff between providing opportunity for anglers to fish for hatchery‐origin steelhead and managing conservation risk for wild steelhead. Understanding population‐level effects of catch‐and‐release fishing is critical for effectively balancing this tradeoff. We used an integrated population model to evaluate population‐level effects of incidental catch‐and‐release mortality on steelhead in Idaho and assessed the effectiveness of alternative management strategies for meeting fishery and population objectives. When simulated catch‐and‐release mortality or encounter rates were low, fishery, abundance, and conservation risk objectives were easily met by implementing fisheries annually, regardless of adult abundance. However, when simulated catch‐and‐release mortality rates were high, management strategies that required the population to surpass minimum thresholds for pre‐season abundance were more likely to meet goals for minimizing conservation risk but limited fishing opportunity substantially. Results of this study provide managers with a framework that can be used to manage fisheries to meet fishery goals in the form of hatchery steelhead harvest while maintaining sustainable populations and minimizing risk to wild steelhead. The results also suggest that when implemented properly, it is possible to meet fisheries and conservation objectives simultaneously. [ABSTRACT FROM AUTHOR]

Stream habitat restoration is an important tool for fisheries management in impaired lotic systems. Although small‐scale benefits of stream habitat restoration are commonly investigated, it is difficult to demonstrate population effects. The Pahsimeroi River Chinook salmon Oncorhynchus tshawytscha population was previously restricted to the lower portion of the river by multiple irrigation structures. To address fish passage issues, a combination of restoration projects was initiated including barrier removals, instream flow enhancements and installation of fish screens on diversions. The largest barrier was removed in 2009, more than doubling the amount of accessible linear habitat. We hypothesized restoration efforts would expand the distribution of spawning salmon in the Pahsimeroi River watershed, leading to a broader distribution of juveniles. We also hypothesized a broader juvenile distribution would have population effects by reducing the prevalence of density‐dependent growth and survival. Redds were documented in newly accessible habitat immediately following barrier removal and accounted for a median of 42% of all redds in the Pahsimeroi River watershed during 2009–2015. Snorkel surveys also documented juvenile rearing in newly accessible habitat. Juvenile productivity increased from a median of 64 smolts/female spawner for brood years 2002–2008 to 99 smolts/female spawner for brood years 2009–2014. Overall, results suggested increased habitat accessibility in the Pahsimeroi River broadened the distribution of spawning adult and rearing juvenile salmon and reduced the effects of density‐dependent survival. Large‐scale stream restoration efforts can have a population effect. Despite the large‐scale effort and response, habitat restoration alone is likely not sufficient to restore this population. [ABSTRACT FROM AUTHOR]

Diversity in steelhead Oncorhynchus mykiss (anadromous Rainbow Trout) is often characterized by varying time spent in freshwater and saltwater environments. However, ontogenetic shifts are not often highlighted as an important diversity characteristic in salmonids. Larger water bodies can play a key role in population stability by buffering limited resources in smaller tributary systems. Based on freshwater and saltwater ages of adult steelhead in Fish Creek, Idaho, there were 12 different life history trajectories observed. Juvenile abundance varied from 12,083 (SE = 1,225.7) to 62,463 (SE = 1,753.8), with ages ranging from young of the year (age 0) to 4 years. Adult abundance fluctuated from 17 (SE < 0.1) to 499 (SE = 67.1), and total age of adults varied from 3 to 7 years. Diversity was most evident in juvenile movement and rearing strategies. We observed four types of movement and rearing pathways in which juveniles either directly migrated to the ocean from Fish Creek or resided for up to three winters in main‐stem river habitat in the Clearwater River basin prior to ocean migration. Most juveniles emigrated in the fall at age 2, and most ocean‐emigrating smolts were age 3. Subsequently, most juveniles resided for at least one additional winter period before ocean migration. Juvenile diversity was also reflected in adult ages; the mean proportion that spent 3 years in freshwater was 0.55 (SE = 0.03), and the mean proportion that spent 2 years in freshwater was 0.41 (SE = 0.03). Adult sex ratio was female biased (mean ± SE = 0.66 ± 0.02), with a higher proportion of females (0.89 ± 0.03) than males (0.65 ± 0.05) residing in the ocean for at least 2 years. Density‐dependent mechanisms were evident in juvenile rearing habitat in Fish Creek for cohorts of high female abundance. Population productivity potentials can be met when tributary and main‐stem rearing habitat can be utilized, and this will be essential in attaining recovery goals. [ABSTRACT FROM AUTHOR]

The "shifting baseline syndrome" (SBS) is the paradigm whereby recent species abundances and environmental conditions are accepted as reflecting historical conditions. This leads to false impressions of the past, inaccurate baselines, and unrealistic recovery goals. Idaho biologists have counted Chinook salmon redds for >60 consecutive years, generating an invaluable database; however, inaccurate historical baselines compromise the utility of even such high-quality, long-term databases. To develop an accurate baseline, we integrated archival (1951–1964), maximum redd counts with contemporary (1995–2017), continuous counts and spawn timing datasets to estimate historical (1950s–1960s) wild Chinook salmon production potential. Current salmon populations average 3% of 1950s–1960s abundances, which may have been 30% of precommercial fishery (1880s) populations. Notably, the SBS has influenced contemporary managers as reflected in minimum viable abundance, sustainable escapement, and adequate seeding objectives equaling 10.4%, 17.9%, and 20.4%, respectively, of 1950s–1960s potential. Our approach provides a framework for utilizing archival and contemporary data to reconstruct historical baselines and repress SBS. Contrasting contemporary goals with maximum production potential provides new reference points and perspectives for managers to consider. [ABSTRACT FROM AUTHOR]

Steelhead Oncorhynchus mykiss is a species that is of high economic value that supports popular sport fisheries across the Pacific Northwest. The Clearwater River in Idaho provides a trophy steelhead fishery, and it is home to both wild‐ and hatchery‐origin steelhead. To manage the fishery effectively, information is needed about the spatial and temporal overlap of wild and hatchery steelhead in the Clearwater River, as well as the activity of anglers. We conducted a radiotelemetry study to describe the distribution of steelhead and their final fate in the Clearwater River, and creel surveys were used to describe the distribution of anglers. In total, 289 wild (Potlatch River and Lochsa River) and hatchery (from Dworshak National Fish Hatchery and South Fork Clearwater River) steelhead were radio‐tagged at Lower Granite Dam, 51 river kilometers (rkm) downstream from the mouth of the Clearwater River. Fish were monitored upon their entry into the Clearwater River by using mobile tracking surveys (boat and vehicle) and stationary antennas. The majority of wild and hatchery steelhead arrived in the Clearwater River in the fall with the exception of those from the Lochsa River, which arrived in the fall and following spring. Average daily movement of the fish was minimal (range = 0.3–4.7 km/d) and dependent on water temperature and flow. The fates of wild and hatchery steelhead varied. Fish returned to spawning grounds, were harvested by anglers (hatchery fish only), or had unknown fates. Both wild and hatchery steelhead returned at high rates to their natal tributaries and release locations. No straying was observed in either group; however, occasions when steelhead have overshot their natal tributaries and release locations were documented. Spatial and temporal overlap of the distributions of wild and hatchery steelhead was minimal. The distribution of anglers overlapped with that of hatchery steelhead in the fall, winter, and spring. The distributional overlap of anglers and wild steelhead was minimal and largely occurred in September in the lower Clearwater River. This suggests that the Clearwater River has a highly compartmentalized fishery and that current fishing regulations in the Clearwater River are providing for a diversity of angling opportunities while conserving wild steelhead and offering harvest of hatchery fish. The results from this study have important implications for the conservation and management of wild and hatchery steelhead. [ABSTRACT FROM AUTHOR]