Benjamin P. Sandford

Survival of juvenile salmonids passing through bypass systems, turbines, and spillways with and without flow deflectors at Snake River dams

Abstract Using yearling chinook salmon Oncorhynchus tshawytscha and steelhead O. mykiss tagged with passive integrated transponders (PITs), we estimated passage survival through bypass systems, turbines, and spill bays with and without flow deflectors at Snake River dams relative to survival of fish released into the tailrace below the dam. Actively migrating fish were collected and marked with PIT tags at Snake River dam smolt collection facilities. Groups of tagged fish were then released through hoses into different passage routes; releases were coincident with a tailrace release approximately 1–2 km below the dam. Relative survival was estimated by the use of tag–recapture models for paired releases from detections of individual PIT-tagged fish at juvenile collection or detection facilities at downstream dams. Detection sites included Little Goose, Lower Monumental, McNary, John Day, and Bonneville dams, depending on the release location and year. Standard errors of relative survival probability estim...

Migration Timing, Growth, and Estimated Parr-to-Smolt Survival Rates of Wild Snake River Spring–Summer Chinook Salmon from the Salmon River Basin, Idaho, to the Lower Snake River

Abstract Survival, growth, and juvenile migration timing are key life history traits for at-risk salmon populations. To estimate these traits in threatened wild Snake River spring–summer Chinook salmon Oncorhynchus tshawytscha, we tagged fish as parr in 3–17 natal streams per year from 1991 to 2003. We injected passive integrated transponder tags into parr collected from streams within the Salmon River basin in Idaho. Each spring, after the previous summers tagging, fish were detected as smolts in the juvenile fish bypass systems of lower Snake River dams. Estimated parr-to-smolt survival to Lower Granite Dam (excluding migration year 1992) ranged from 3% to 48% for individual populations and from 8% to 25% (yearly average = 16%) for all streams combined. From 1998 to 2004, estimated parr-to-smolt survival declined from 25% to 8%, in part because of parr density-dependent effects. Overall annual average growth rates from tagging to detection at Little Goose Dam ranged from 39.7 to 43.3 mm during 2001–200...

Post-Hydropower System Delayed Mortality of Transported Snake River Stream-Type Chinook Salmon: Unraveling the Mystery

Abstract Past research indicates that on an annual basis, smolts of stream-type Chinook salmon Oncorhynchus tshawytscha collected at Snake River dams and transported by barge to below Bonneville Dam have greater post-hydropower system mortality than smolts that migrate in-river. To date, this difference has most commonly been attributed to stress from collection and transportation, leading to decreased disease resistance or predator avoidance ability. Using both hatchery and wild passive integrated transponder (PIT) tagged Chinook salmon, we explored two mechanisms that either separately or jointly contributed to an alternative explanation: Altered timing of ocean entry and lost growth opportunity leading to size-selective predation. Based on weekly estimates of in-river survival and adult return rates of smolts that were transported or that migrated in-river between Lower Granite and Bonneville dams, we found greater post-hydropower system mortality for smolts transported early in the season but greater ...

Evidence of Delayed Mortality on Juvenile Pacific Salmon Passing through Turbines at Columbia River Dams

Abstract We evaluated the survival of juvenile salmon through turbines in Columbia River dams and found no differences between two operations but strong evidence of delayed mortality from turbine passage. After tagging with a passive integrated transponder (PIT) tag and a radio tag, yearling Chinook salmon Oncorhynchus tshawytscha were released at McNary Dam on the Columbia River through a turbine operating both within 1% of peak efficiency (a discharge rate of 317 m3/s) and outside the 1% range at the maximum blade angle (464 m3/s). Estimated relative survival to a detection array 15 km downstream was 0.871 at 317 m3/s and 0.856 at 464 m3/s and 0.858 and 0.814, respectively, to an array 46 km downstream. The highest point estimates of survival occurred under the lower discharge, suggesting that operating turbines within 1% of peak efficiency is a useful guideline for fish protection at McNary Dam. In a concurrent evaluation using balloon tags, estimated mean direct survival ranged from 0.930 to 0.946. Ra...

Estimation of smolt-to-adult return percentages for Snake River Basin anadromous salmonids, 1990–1997

From numbers of juvenile salmonids (smolts) tagged between 1990 and 1997 with passive-integrated-transponder (PIT) tags and detections at downstream hydropower projects on the lower Snake and Columbia Rivers, we applied and adapted stratified tagrecapture methods to estimate the number of PIT-tagged smolts that experienced each possible detection history through the dams. Using adult detection recordsupon, return after 1–3 years of ocean residence, we estimated smolt-to-adult return (SAR) percentages for fish in detection-history categories that included downstream barge transport, migration in-river following detection, and migration in-river with no detection. We used bootstrap methods to estimate 95% confidence intervals for estimated SARs and ratios of SARs for selected detection-history categories. In general, though small numbers of returning adults and statistical uncertainty at various stages of the estimation procedure led to fairly imprecise SAR estimates, some general trends were evident. Adult return percentages for spring/summer yearling chinook salmon and steelhead were highest for fish transported from Lower Granite and Little Goose Dams but only slightly higher than for nondetected fish. Passage routes of nondetected fish (through spill and turbines) may represent optimal passage conditions. Once a juvenile fish is entrained in a bypass system ata “collectordam,” transporting the fish maximizes the probability of its eventual return as an adult.

A Comparison of Migration Rates of Radio- and PIT-Tagged Adult Snake River Chinook Salmon through the Columbia River Hydropower System

Abstract Documentation of adult salmonid migration behavior in the Columbia River drainage is critically needed to assess the effects of dams on travel time and passage. In 2000, we compared the upstream travel times of passive integrated transponder (PIT)-tagged and radio-tagged adult chinook salmon Oncorhynchus tshawytscha from Bonneville Dam on the lower Columbia River to Lower Granite Dam on the Snake River. We found no evidence that radio tagging negatively affected chinook salmon behavior. In fact, their median travel time (14.1 d, range = 7.8-44.4 d, N = 113) was actually faster (statistically significant at P = 0.005) than that for PIT-tagged fish (median = 15.9 d, range = 8.9-67.4 d, N = 164) after accounting for temporal effects (i.e., Bonneville Dam passage date). However, we concluded this difference was not biologically significant and was probably related to differences in study design or data complications. This study indicated that radio transmitters weighing less than 2% of chinook salmon...

Diversion of Salmonid Smolts Tagged with Passive Integrated Transponders from an Untagged Population Passing through a Juvenile Collection System

Abstract We evaluated a system to divert salmonid smolts tagged with passive integrated transponders (PIT) from the general migrant population as they passed through a juvenile collection system at a hydroelectric dam on the Snake River. Our goal was to maximize the diversion of PIT-tagged fish while simultaneously minimizing the diversion of untagged fish. The slide-gate system that was tested diverted 81% of PIT-tagged fish detected. The number of untagged fish entering the diversion system with every PIT-tagged fish was proportional to fish abundance and averaged one untagged fish for every PIT-tagged fish. Measures of descaling, injury, and mortality for all fish in the diversion system were similar to those for fish that were not diverted. These results established our basic PIT-tag diversion system as a major tool for conducting research on Snake River anadromous salmonids.

Bypass System Modification at Bonneville Dam on the Columbia River Improved the Survival of Juvenile Salmon

Abstract From 1987 to 1992, we evaluated a fish bypass system at Bonneville Dam Powerhouse 2 on the Columbia River. The survival of subyearling Chinook salmon Oncorhynchus tshawytscha released into the system ranged from 0.774 to 0.911 and was significantly lower than the survival of test fish released into turbines and the area immediately below the powerhouse where bypass system flow reentered the river. Yearling and subyearling Chinook salmon and yearling coho salmon O. kisutch released into the bypass system were injured or descaled. Also, levels of blood plasma cortisol and lactate were significantly higher in yearling and subyearling Chinook salmon that passed through the bypass system than in fish released directly into a net located over the bypass exit. This original system was then extensively modified using updated design criteria, and the site where juvenile fish reentered the river was relocated 2.8 km further downstream to reduce predation on bypassed fish by northern pikeminnow Ptychocheilu...

Relationship of external fish condition to pathogen prevalence and out-migration survival in juvenile steelhead

Abstract Understanding how the external condition of juvenile salmonids is associated with internal measures of health and subsequent out-migration survival can be valuable for population monitoring programs. This study investigated the use of a rapid, nonlethal, external examination to assess the condition of run-of-the-river juvenile steelhead Oncorhynchus mykiss migrating from the Snake River to the Pacific Ocean. We compared the external condition (e.g., body injuries, descaling, external signs of disease, fin damage, and ectoparasite infestations) with (1) the internal condition of a steelhead as measured by the presence of selected pathogens detected by histopathology and polymerase chain reaction analysis and (2) out-migration survival through the Snake and Columbia rivers as determined by passive integrated transponder (PIT) tag technology. The results from steelhead captured and euthanized (n = 222) at Lower Monumental Dam on the lower Snake River in 2008 indicated that external condition was sig...

Disease Susceptibility of Hatchery Snake River Spring–Summer Chinook Salmon with Different Juvenile Migration Histories in the Columbia River

Various methods have been developed to mitigate the effects of dams on juvenile Pacific salmon Oncorhynchus spp. migrating to the Pacific Ocean through the Columbia River basin. In this study, we examined the health of hatchery Snake River spring and summer Chinook salmon relative to two mitigating strategies: dam bypass and transportation (e.g., barging). The health of out-migrants was assessed in terms of the difference in the incidence of mortality among fish, categorically grouped into no-bypass, bypass, and transportation life histories, in response to challenge with the marine pathogen Listonella anguillarum during seawater holding. These three life histories were defined as follows: (1) fish that were not detected at any of the juvenile bypass systems above Bonneville Dam were classified as having a no-bypass life history; (2) fish that were detected at one or more juvenile bypass systems above Bonneville Dam were classified as having a bypass life history; and (3) fish that were barged were classified as having the transportation life history. Barged fish were found to be less susceptible to L. anguillarum than in-river fish-whether bypassed or not-which suggests that transportation may help mitigate the adverse health effects of the hydropower system of the Columbia River basin on Snake River spring-summer Chinook salmon. The findings of this study are not necessarily transferable to other out-migrant stocks in the Columbia River basin, given that only one evolutionarily significant unit, that is, Snake River spring-summer Chinook salmon, was used in this study.