Hatcheries in the U.S. Pacific Northwest are increasingly implementing programs that use an adipose fin clip and coded wire tag to mark a large number of juvenile salmonids Oncorhynchus spp. Traditionally, fin‐clipping and tagging were done by hand, but the need to mass‐mark large numbers of fish has led to the development of an automated tagging trailer system (Northwest Marine Technology, Inc.). We compared the adipose fin clip quality, coded wire tag retention, and injury rates of juvenile stream‐type spring Chinook salmon O. tshawytscha marked and tagged at automated and manual tagging trailers at Warm Springs National Fish Hatchery (NFH) and Carson NFH, two hatcheries located in the Columbia River basin. Clip quality (99% good clips), tag retention (>98%), and injury rates (<7%) were similar between the two types of trailers at Carson NFH, where the manual markers had several years' experience clipping and tagging fish. At Warm Springs NFH, where the majority of manual markers had no previous experience, injury rates were similar (<14%) but the fish marked and tagged in the automated trailer had significantly higher clip quality (95% good clips) and tag retention (98%) than those marked and tagged in the manual trailer (70% good clips, 87% retention), where the clip quality and tag retention were poorest during the first day of tagging. Our results show that automated and manual trailers can perform similarly with regard to fin clip quality, tag retention rate, and injury rate when staffed by experienced markers. We recommend focusing efforts on training and quality control during the initial days of tagging and incorporating postmarking clip quality and coded wire tag retention sampling into all marking programs.

Removal of fish passage barriers provides Pacific salmon Oncorhynchus spp. and steelhead O. mykiss the opportunity to recolonize previously accessible habitat, though the time scale of natural recolonization may not be sufficient for management or conservation goals. One strategy for accelerating recolonization is to outplant hatchery‐origin adults into newly restored habitats. In this paper, we describe how genetic parentage analysis was used to determine the reproductive success of adult stream‐type spring Chinook salmon O. tshawytscha taken from two localized hatchery stocks and outplanted into a stream. We defined reproductive success as the production of migratory juveniles. In 2002 and 2003, 83 and 265 adult hatchery salmon, respectively, were outplanted into Shitike Creek, Oregon, a tributary to the Deschutes River. Using 11 microsatellite markers, 799 and 827 migratory juveniles from the two brood years were genotyped and matched back to potential outplanted parents using genetic parentage analyses. Successful spawning of outplant–outplant, outplant–wild, and wild–wild fish occurred in Shitike Creek in both years. Adults outplanted in 2002 showed far fewer matches (18%) to sampled juveniles than those from 2003 (88%). Additionally, only 1% of juveniles had both parents identified as outplants in 2002, compared with almost 61% in 2003. Differences in the number of females outplanted each year appeared to account for the differential productivity. The number of offspring attributed to an individual outplant was variable, ranging from 1 to more than 10. Multiple outplant × outplant matings were identified for each sex as males mated with up to seven females and females mated with up to four males. This study shows that, under the right conditions, outplanted adult hatchery fish taken from localized hatchery stocks can contribute to the overall juvenile production in a natural stream.

Juvenile winter steelhead Oncorhynchus mykiss at Eagle Creek National Fish Hatchery in Estacada, Oregon, were reared for three brood years (2004–2006) at raceway densities of 7,500 (214 fish/m3), 15,000 (429 fish/m3), and 22,500 fish (643 fish/m3) to determine the effects of rearing density on growth, fin erosion, survival, adult yield, and migration behavior. Coded wire tags were used to evaluate adult survival, and fish were radio‐tagged to monitor migration times from the hatchery to the mouth of Eagle Creek following volitional release from the hatchery. We found rearing density had a significant effect (P < 0.05) on steelhead growth, fin erosion, and adult survival. Winter steelhead reared in low‐density raceways (13.6 kg/m3 at release) were significantly larger at release, larger at return, had significantly better dorsal fin condition, and had significantly greater smolt‐to‐adult survival rates than did those reared in medium (23.4 kg/m3) and high (35.2 kg/m3) density raceways. No significant relationship between smolt size at release and migration timing was detected; however, the effect of rearing density on fish migration was noticeable in brood year 2004. In that year (2004), smolts from the medium‐ and high‐density groups took from 6 to15 d longer to out‐migrate than those from the low‐density group.

We evaluated growth and survival of spring Chinook salmon Oncorhynchus tshawytscha reared at varying densities at Warm Springs National Fish Hatchery, Oregon. For three consecutive brood years, density treatments consisted of low, medium, and high groups in 57.8-m3 raceways with approximately 16,000, 24,000, and 32,000 fish/raceway, respectively. Fish were volitionally released in both the autumn and spring to mimic the downstream migration timing of the endemic wild spring Chinook salmon stock. Just prior to the autumn release, the rearing density estimate was 4.24 kg/m3 for the low-density group, 6.27 kg/m3 for the medium-density group, and 8.42 kg/m3 for the high-density group. While weight gain did not differ among density treatments (P  =  0.72), significant differences were found in median fork length (P &lt; 0.001) for fish reared at different densities. Fish reared at high density exhibited the highest on-hatchery mortality rate during two brood years; however, differences in mortality rate among densities were not significant (P  =  0.20). In one brood year, adult recovery rates appeared to support the hypothesis that lower initial densities improved postrelease survival (P &lt; 0.01). All rearing densities utilized in this evaluation were relatively low and may partially explain why more differences were not readily apparent among density groups. In addition, the volitional release was a confounding factor in our study because we were unable to quantify the number of fish released in the autumn.

Direct underwater observation techniques (e.g., snorkel surveys) are widely used in fisheries science. Data collected from these surveys are used to estimate species abundance, detect presence and absence, and construct statistical models that predict microhabitat use and nonuse. To produce an unbiased estimate or model, fish should ideally behave as if there were no observer present. We conducted a study using underwater video to test whether snorkeling can elicit a change in fish behavior. Four behavioral metrics were measured: upstream movement, downstream movement, total movement, and number of fish in the field-of-view. Significant differences were detected in upstream, downstream, and total movements as a function of the in-water observer. These results suggest that an in-water observer can disturb fish, resulting in altered behavior, which in turn may bias study results. We suggest researchers use caution in making inferences to an entire population when data-collection methods have potential to bias fish behavior.