Adult Steelhead Research Articles

Comparisons of Run Timing, Spatial Distribution, and Length of Wild and Newly Established Hatchery Populations of Steelhead in Forks Creek, Washington

In Washington State, the approach to management of wild and hatchery steelhead trout Oncorhynchus mykiss has been to separate the timing of return and spawning by the two groups through selective breeding for early timing in hatchery fish. However, overlap in timing and spatial distribution could permit genetic and ecological interactions. To evaluate this management approach, we compared the timing, spatial distribution, and size of adult steelhead in the wild and newly established hatchery populations of Forks Creek, Washington. Hatchery fish tended to return and spawn about 3 months before wild fish but there was some temporal overlap. Radio-tracking indicated that the spatial distributions of the populations overlapped considerably, permitting interbreeding and ecological interactions. However, the hatchery fish tended to stay closer to the hatchery, consistent with olfactory imprinting on the hatchery's water supply. Wild females were larger than hatchery females (median fork lengths were 670 and 644 mm, respectively), and wild males and females varied more in length than did hatchery fish of the same sex. In the first year in which naturally spawned offspring of hatchery fish might have returned, we observed a marked increase in early-returning unmarked (i.e., naturally spawned) adults, suggesting that some hatchery fish spawned successfully in the creek.

Genetic structure and relationships among steelhead trout (Oncorhynchus mykiss) populations in British Columbia.

Steelhead trout, Oncorhynchus mykiss (the anadromous form of rainbow trout), are declining over much of their range around the Pacific rim. We nondestructively collected tissue samples from 494 adult steelhead from eight tributaries and two mainstem river sites within three watersheds in northern British Columbia, Canada. We scored allele size for six highly polymorphic microsatellite DNA loci and provide primer sequences and polymerase chain reaction conditions for five of these loci for the first time. The populations were significantly genetically differentiated (theta = 0.039; 95% confidence = 0.030-0.053). AMOVA showed that most of the genetic variation was at the individual level (95.6%), although significant genetic variation existed at the tributary level (3.09%) and watershed level (1.31%). The calculated unbiased genetic distances were positively correlated with geographical distance within watersheds (P < 0.01; r(2)=0.35) indicating probable genetic equilibrium. Tributary populations in two of the watersheds were not as genetically divergent as would be expected given their large geographical separation. Cross-headwater transfers of fish within relatively recent history are the most likely explanation of this anomaly. Seven of the eight tributary populations fit a regression line of mean heterozygosity vs. rearing habitat area. The one anomalous population had a much lower heterozygosity than expected based on the linear regression, and may thus be the population of greatest conservation concern.

Low Adult Return of Juvenile Steelhead Treated with 17α-Methyltestosterone to Produce Sterility

Abstract Juvenile hatchery summer steelhead Oncorhynchus mykiss were treated with the hormone 17α-methyltestosterone by methods developed for rainbow trout O. mykiss in an attempt to obtain sterile returning adults. Our objective was to determine if sterile steelhead would return to a target stream at frequencies high enough to provide recreational fisheries while providing fishery managers with a tool for reducing steelhead interactions with wild fish. From three brood years of treated releases, only one sterile adult steelhead returned to the collection hatchery on the South Santiam River, Oregon. Gonads were absent in this fish at the end of spawning in February. Other returning adults from treatment groups were 80% male and 20% female. Adults from control groups were 49% male and 51% female. Males from treatment groups developed secondary sexual characteristics similar to controls but contained deformed gonads at the end of spawning. Gonads of treated females appeared normal, but only one ripened by t...

Influence of Water Temperature in Use of Deep Pools by Summer Steelhead in Steamboat Creek, Oregon (USA)

This study examined use of deep pools (>0.8 m mean depth) based on thermal characteristics by adult summer steelhead in Steamboat Creek, Oregon. Steamboat Creek had a heterogenous thermal profile, with some segments exceeding the preferred temperature of steelhead. Deep pools were scarce (4% of the total habitat types), and 39% of them were identified as cool pools (mean bottom water temperature 19°C). Adult summer steelhead were found primarily in deep pools, avoiding other habitats such as glides, riffles, and even cool tributary junctions. Adult abundance in deep pools did not show significant variation between years and was inversely associated with mean bottom temperature. Use of cool pools was estimated to be 11 times the use of warm pools. However, the presence of unoccupied cool pools suggested that other ecological variables may be involved in pool selection.

Trends in wild adult steelhead (Oncorhynchus mykiss) abundance for snowmelt-driven watersheds of British Columbia in relation to freshwater discharge

Snowmelt-driven rivers of British Columbia support primarily summer-run steelhead (Oncorhynchus mykiss) that may spend up to 5 years as juveniles in freshwater. Time series analyses revealed significant negative correlations between an annual index of wild adult steelhead abundance (catch-per-angler-day, CpAD) for these rivers and summer freshwater discharge when these steelhead were juveniles. The strength of these relationships was related to latitude, with the more northerly rivers generating the strongest relationship between CpAD and freshwater discharge. Potential mechanisms by which interannual variation in freshwater discharge can modulate adult steelhead abundance include reduced juvenile mortality due to lower flow velocities during the warm summer months and to the creation of more juvenile habitat in low-velocity refuges. Alternatively, interannual variability in adult steelhead abundance is driven by variability in ocean climate of which freshwater discharge is an index. Interpretation of the data and analyses was encumbered in part by particular factors affecting CpAD as an index of abundance. However, the analyses support an interpretation that steelhead survival to adulthood might be influenced by freshwater conditions more so in northern snowmelt-driven rivers than in rainfall-driven rivers because steelhead from those rivers spend more years in freshwater as juveniles.

Trends in wild adult steelhead (Oncorhynchus mykiss) abundance in British Columbia as indexed by angler success

Intraregional similarities and interregional differences in wild steelhead (Oncorhynchus mykiss) abundance trends over time throughout British Columbia were identified using catch-per-angler-day (CpAD) as an index of abundance. This index was calculated using sport angler catch and effort data obtained by an ongoing mail-out questionnaire begun in the fiscal year 1967-1968. Despite high interannual variability in CpAD for individual rivers, its validity as an index of trends over time in wild steelhead abundance for geographic regions or watersheds is reinforced by similar trends yielded by both fishery-dependent and fishery-independent data. Time series methods generally could not build statistical support for the hypotheses that sudden regulation changes, or the gradual introduction over time of a catch and release philosophy, are generally important factors affecting trends over time in CpAD. This bolsters our confidence that the general patterns in mean CpAD over time within regions and watersheds reasonably index actual wild adult in-river steelhead abundance. We propose that the trends that we observe in wild steelhead CpAD are primarily driven by environmental influences. Some candidate environmental time series currently being considered and investigated are coastal upwelling, various ocean and atmospheric climate indices, freshwater discharge histories, and ultraviolet radiation.

Trends in wild adult steelhead (Oncorhynchus mykiss) abundance for coastal regions of British Columbia support the variable marine survival hypothesis

Wild adult steelhead (Oncorhynchus mykiss) abundance for rivers in British Columbia was indexed using catch-per-angler-day (CpAD) calculated from data obtained using an angler questionnaire. Mean annual CpAD for primarily winter-run steelhead in rivers of four rainfall-driven coastal regions of British Columbia showed similar trends from the fiscal year 1967-1968 to 1989-1990. After 1989-1990 the trends diverged. The generally remote rivers of the west coast of Vancouver Island and the Queen Charlotte Islands maintained a steady or increasing trend in CpAD after 1989-1990. The long-term trend for these two regions correlated well with a joint index of winter and summer upwelling for the Coastal Upwelling Domain for the years that steelhead are at sea and is consistent with studies that relate marine survival of salmon to oceanic-atmospheric climate. In contrast with west coast Vancouver Island and the Queen Charlotte Islands, most rivers of the east coast of Vancouver Island and the lower mainland near Vancouver revealed declining trends since 1989-1990. Most of these rivers drain into the Strait of Georgia. Reasons for the discrepancy among regions after about 1990 are discussed. They include high angling pressure related to hatchery supplementation, differences in riverine and marine conditions, and smolt migration distance.

Trends in wild adult steelhead (&lt;i&gt;Oncorhynchus mykiss&lt;/i&gt;) abundance for coastal regions of British Columbia support the variable marine survival hypothesis

Wild adult steelhead (Oncorhynchus mykiss) abundance for rivers in British Columbia was indexed using catch-per-angler-day (CpAD) calculated from data obtained using an angler questionnaire. Mean annual CpAD for primarily winter-run steelhead in rivers of four rainfall-driven coastal regions of British Columbia showed similar trends from the fiscal year 1967-1968 to 1989-1990. After 1989-1990 the trends diverged. The generally remote rivers of the west coast of Vancouver Island and the Queen Charlotte Islands maintained a steady or increasing trend in CpAD after 1989-1990. The long-term trend for these two regions correlated well with a joint index of winter and summer upwelling for the Coastal Upwelling Domain for the years that steelhead are at sea and is consistent with studies that relate marine survival of salmon to oceanic-atmospheric climate. In contrast with west coast Vancouver Island and the Queen Charlotte Islands, most rivers of the east coast of Vancouver Island and the lower mainland near Vancouver revealed declining trends since 1989-1990. Most of these rivers drain into the Strait of Georgia. Reasons for the discrepancy among regions after about 1990 are discussed. They include high angling pressure related to hatchery supplementation, differences in riverine and marine conditions, and smolt migration distance.

Trends in wild adult steelhead (&lt;i&gt;Oncorhynchus mykiss&lt;/i&gt;) abundance for snowmelt-driven watersheds of British Columbia in relation to freshwater discharge

Trends in wild adult steelhead (&lt;i&gt;Oncorhynchus mykiss&lt;/i&gt;) abundance for snowmelt-driven watersheds of British Columbia in relation to freshwater discharge

Trends in wild adult steelhead (&lt;i&gt;Oncorhynchus mykiss&lt;/i&gt;) abundance in British Columbia as indexed by angler success

Trends in wild adult steelhead (&lt;i&gt;Oncorhynchus mykiss&lt;/i&gt;) abundance in British Columbia as indexed by angler success

Allozyme Studies of Pacific Salmonids with Nonlethal Sampling of Fin Tissue

We evaluated the use of nonlethal sampling of bony fin tissue to obtain allozyme data for Pacific salmonids Oncorhynchus spp. Enzyme activity was detected for 53 loci, including many polymorphic loci, in caudal fin tissue sampled from chinook salmon O. tshawytscha, chum salmon O. keta, coho salmon O. kisutch, sockeye salmon O. nerka, and steelhead O. mykiss. This represents 61% of all the loci (N = 87) routinely analyzed using eye, heart, liver, and muscle tissue. Anal, dorsal, caudal, pelvic, and pectoral fin tissues all expressed the same loci with approximately the same strength of activity. Fin tissue sampled from adult salmonids yielded a slightly greater number of loci than did juvenile samples. Sufficient allozyme activity was observed for 9 mg of juvenile chinook salmon and steelhead fin tissue for some loci; however, the minimal amount of tissue needed to obtain all detectable loci was 54 mg. We performed computer simulations to test the feasibility of using allozyme data from fin tissue in mixed-stock analyses. The simulations showed that using the loci expressed in fin tissue samples, we were able to accurately estimate the stock composition of adult steelhead migrating up the Columbia River. Fin tissue sampling will be useful for collecting allozyme data when other tissues are not available or when lethal sampling is not desirable and will complement mitochondrial and nuclear DNA techniques that also use nonlethal sampling.

Vaccination of Rainbow Trout against Infectious Hematopoietic Necrosis (IHN) by Using Attenuated Mutants Selected by Neutralizing Monoclonal Antibodies

Abstract A neutralizing monoclonal antibody against infectious hematopoietic necrosis virus (IHNV) was used to select neutralization-resistant mutants from isolates of virus obtained from adult steelhead Oncorhynchus mykiss returning to the Round Butte Hatchery (RB mutants) on the Deschutes River in Oregon, USA, and from rainbow trout (nonanadromous O. mykiss) at a commercial hatchery in the Hagerman Valley of Idaho, USA (193-110 mutants). Two of the mutants, RB-1 and 193-110-4, were significantly (P < 0.001) attenuated compared with parental strains. Vaccination of rainbow trout by waterborne exposure to the mutants conferred solid protection against challenge with wild-type virus. In some trials, fish vaccinated with the RB-1 mutant at 50% tissue culture infectious doses (TCID50) of 1 × 104–1 × 105 TCID50/mL or with the 193-110-4 mutant at 1 × 102–1 × 103 TCID50/mL, held for 14 d, then challenged with the homologous wild-type strain at 1 × 105 TCID50/mL showed relative percent survival of 95–100% (P < 0...

Bayesian Averaging of Generalized Linear Models for Passive Integrated Transponder Tag Recoveries from Salmonids in the Snake River

Abstract Bayesian methods provide a means of explicitly accounting for uncertainty in the choice of model used to interpret fisheries data. The probability of a given model being the correct model conditional on the data, the posterior probability, is a measure of the degree of belief and strength of evidence for the model. Bayesian model averaging uses these posterior probabilities to make weighted inferences, thus providing a solution to the problem of selecting a single model from a group of models that seem nearly equivalent by conventional statistical criteria. The approach is applied to a generalized linear model analysis of survival for juvenile and mature adult spring chinook salmon Oncorhynchus tshawytscha and steelhead Oncorhynchus mykiss from the Snake River. The fish, tagged as juveniles with passive integrated transponders (PIT), outmigrated from freshwater habitat to the ocean during 1989–1991, and include some of the first PIT tag recoveries of adult fish. Covariates used to model survival ...

Survival of Electroanesthetized Adult Steelhead and Eggs of Fall Chinook Salmon

Abstract We evaluated the effects of the Coffelt system 91 electroanesthesia unit on survival of adult steelhead Oncorhynchus mykiss and the egg-to-fry stages of fall chinook salmon O. tshawytscha. Adult steelhead were anesthetized at one of several voltages with the complex pulse pattern from the system 91 or with carbon dioxide gas. Fish were then tagged, transported, and released. Tags were recovered at two hatcheries and by recreational anglers. An average of 39% of electroshocked fish and 46% of fish anesthetized with carbon dioxide were recovered. However, tags from both groups were returned at similar rates by recreational anglers. Recovery rate differences appeared to be reduced at 50 and 80 V. Egg-to-fry mortality for progeny of electroanesthetized fall chinook salmon averaged 7%, compared with 12% for control groups. We conclude that if low levels of fish damage are acceptable, electroanesthesia may be a viable alternative to other anesthetics.

Characteristics of Pools Used by Adult Summer Steelhead Oversummering in the New River, California

Abstract I assessed characteristics of pools used by oversummering adults of summer steelhead Oncorhynchus mykiss between July and October 1991 in the New River, northwestern California. Most fish occupied channel confluence pools and other pools of moderate size (200–1,200 m2); these pools had less than 35% substrate embeddedness and mean water depths of about 1.0–1.4 m. Microhabitat occupied during daylight hours included cover provided by bedrock ledges and boulders where water velocity averaged 9.3 cm/s (range, 1–34 cm/s); steelhead densities under this cover were highest at the higher velocities. Fish also occupied areas with riparian shading and waters deeper than 1 m. I observed localized areas of cool water in some of the study pools. The availability of coolwater areas in pools did not increase adult fish use of those pools. The results of this study indicate that the distribution of summer steelhead in the New River during July–October is more strongly controlled by physical habitat characterist...

Thermally Stratified Pools and Their Use by Steelhead in Northern California Streams

Thermal stratification occurred in pools of three rivers in northern California when inflow of cold water was sufficiently great or currents were sufficiently weak to prevent thorough mixing of water of contrasting temperatures. Surface water temperatures in such pools were commonly 3–9°C higher than those at the bottom. Cold water entered pools from tributaries, intergravel flow through river bars, and streamside subsurface sources. In Redwood and Rancheria Creeks, cold water was protected where gravel bars encroached into pools that were scoured along bedrock banks, creating isolated backwaters. Sixty-five percent of the juvenile steelhead Oncorhynchus mykiss found in the Rancheria Creek study reaches moved into adjacent stratified pools during periods of high ambient stream temperatures (23–28°C). Fish showed a decline in forage behavior and increased agonistic activity just before movement into stratified pools. In the Middle Fork Eel River, pools deeper than 3 m stratified when surface flow decreased to less than 1 m3/s. Summer-run steelhead adults were found in deep stratified pools on the Middle Fork Eel River throughout summer when midday ambient stream temperatures ranged from 26 to 29°C and coldwater pockets averaged 3.5°C cooler. Thermally stratified pools provided refuge habitat for significant numbers of young-of-the-year, yearling, and adult steelhead in marginal river habitats where stream temperatures reach upper incipient lethal levels.

Passive Monitoring of Migrating Adult Steelhead with PIT Tags

In 1985, two independent passive integrated transponder (PIT) tag monitoring systems were installed at the exit area of the weir leading into a fish trap on the north-shore fish ladder at Bonneville Dam, Columbia River. One hundred PIT-tagged adult steelhead Oncorhynchus mykiss were released in groups of 10 into an enclosed area of the ladder downstream from the detectors. The tagged fish were detected after they volitionally swam through the weir and slid through the detection system at velocities of 0.6 m/s or greater. Overall PIT tag reading efficiency was 98% and no tag-reading errors were recorded. Individual tag code, date, and time of the passage of each tagged fish were automatically recorded into a computer file and simultaneously printed onto a paper copy. These results suggest that PIT tag monitors of this design could be deployed at select adult passage facilities presently operating in the Columbia River Basin to interrogate returning PIT-tagged adult salmonids.

Returns of Hatchery Steelhead Relative to Site of Release below an Upper-River Hatchery

Steelhead smolts Oncorhynchus mykiss reared at the Chilliwack River Hatchery in southwestern British Columbia were tagged, transported, and released at four (1982) or six (1983, 1984) locations along the Chilliwack River. Returning adults were recovered from the sport fishery within three 10-km reaches (lower, middle, and upper) situated downstream of the upper-river hatchery. Percent recoveries were highly correlated with mean smolt size at stocking (range, 61–115 g), and most returning adults were caught within the lower river. There were small but significant effects of release location on the distribution of adult steelhead recoveries in two of three reaches. Within the lower-river catch of adults, the percentage of all lower-release recoveries was 10.3 percentage points higher than the percentage of all middle-release recoveries and 10.7 points higher than the percentage of all upper-release recoveries. In the upper-river catch, the percentage of all upper-release recoveries was 5.5 and 11.4 points higher than the percentage of all middle- and lower-release recoveries, respectively. Middle-river recoveries were not disproportionately higher for any release-reach group. Similarly, among adults that returned to the hatchery channels in the upper river, on average, 43% were from the upper, 30% from the middle, and 27% from the lower reaches of release; thus, homing was strongly influenced by the rearing location. In a steelhead fishery associated with an upper-river hatchery and dependent on wild and hatchery-reared fish, transport and release of smolts affected homing of adults, but there was substantial dispersal of lower-river fish to the upper river. These findings have implications for selective management of augmented steelhead stocks.

Horizontal and Vertical Movements of Adult Steelhead Trout, Oncorhynchus mykiss, in the Dean and Fisher Channels, British Columbia

Horizontal and vertical movements of adults steelhead trout, Oncorhynchus mykiss, in the Dean and Fisher channels, British Columbia, were examined using radio and ultrasonic telemetry. Nineteen steelhead, captured by purse seine in 1987 and fitted with radio tags, averaged 17.2 ± 2.2 (SE) km/d to travel 96.4 km from the capture/release site to the Dean River mouth. Detailed movement patterns were assessed from six steelhead tracked for 224 h (21.0–49.8 h/fish) using ultrasonic tags in 1988. Gross and net travel rates of steelhead averaged 2.0 and 0.8 km/h, respectively, indicating considerable milling by the fish. Gross movement during daylight [Formula: see text] was twice that during the night [Formula: see text] and most movement at night was attributed to tidal currents. The steelhead swam primarily on the surface throughout the fjord, regardless of salinity and temperature stratification. Geometric mean depth was 1.6 m and the fish spent, on average, 72% of the time in the top 1 m (the warmest and least saline water available). Median time between dives to 5 m (near the halocline) was 9 min, although 14% of the surface intervals exceeded 1 h. These results are discussed in relation to several hypotheses regarding guidance mechanisms used by migrating fishes.

Biochemical and Antigenic Properties of the First Isolates of Infectious Hematopoietic Necrosis Virus from Salmonid Fish in Europe

Abstract The first isolates of infectious hematopoietic necrosis virus (IHNV) recovered from rainbow trout Oncorhynchus mykiss (formerly Salmo gairdneri) in France and Italy were compared to six representative strains from North America by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of virion polypeptides and neutralization by monoclonal antibodies (MAbs). All three IHNV isolates from Europe had similar polypeptide profiles when compared by SDS-PAGE. An analysis of the antigenic relatedness of the European isolates to representative strains from North America showed that they were clearly different from viruses obtained from salmonids in California. The RB/B5 MAb, which was developed against virus isolated from adult steelhead (anadromous rainbow trout) reared in central Oregon, neutralized all isolates examined. The 193–110/B4 MAb, developed against IHNV isolated from infected yearling rainbow trout in southern Idaho, neutralized all isolates tested except those from California. ...