The short-term survival rate of hatchery-reared fall yearling chinook salmon smolts (Oncorhynchus tshawytscha) introduced at 3.1 m below the turbine intake ceiling (N = 350) at a large Columbia River hydroelectric dam relative to the survival rate of controls (released in the discharge) was estimated at 93.0% (90% profile CI = 90.1-95.5%); among those introduced at 9.3 m depth (N = 250) the survival rate was 94.7% (90% CI = 91.9-97.0%). Differences were not significant, and the pooled estimate of 93.9% (90% CI = 91.9-95.7%) is higher than is generally assumed or reported (70-89%) for salmonids. Unlike the prevailing models based on recovery ratios of alive fish only, our likelihood model included the capture probabilities of both the alive and dead fish for estimation of parameters and their standard errors. Survival rates reported herein refer to the direct effects of turbine passage; those reported in the literature, however, do not make a clear distinction between direct (immediately upon turbine passage) and indirect effects that may occur over time. The types of fatal injuries observed suggested that a reduction or elimination of gaps between the hub and runner blades may enhance fish survival.Résumé : On a estimé à 93,0% (profil à 90% : IC = 90,1-95,5%) le taux de survie à court terme de smolts de saumons quinnats d'automne (Oncorhynchus tshawytscha) élevés en pisciculture, introduits à 3,1 m sous la partie supérieure d'une prise d'eau de turbine (N = 350) d'un important barrage hydro-électrique du fleuve Columbia, par rapport à celui de témoins (libérés dans le déversoir); chez les smolts introduits à une profondeur de 9,3 m (N = 250), le taux de survie était de 94,7% (profil à 90% : IC = 91,9-97,0%). Les différences n'étaient pas significatives, et la valeur estimée combinée, de 93,9% (profil à 90 % : IC = 91,9-95,7%), est supérieure à celles qui sont généralement supposées ou signalées (70-89%) pour les salmonidés. À la différence des modèles les plus courants basés sur les rapports de récupération des poissons vivants seulement, notre modèle de vraisemblance prévoit les probabilités de prise des poissons vivants ou morts pour l'évaluation des paramètres et de leur écart-type. Les taux de survie signalés ici correspondent aux effets directs du passage dans la turbine; toutefois, ceux qui sont indiqués dans la littérature ne font pas une distinction très nette entre les effets directs (immédiatement après le passage dans la turbine) et les effets indirects qui surviennent plus tard. Les types de blessures mortelles observés laissent croire que la réduction (ou l'élimination) des espaces vides entre l'axe et les pales mobiles pourrait améliorer les chances de survie des poissons. [Traduit par la Rédaction]

A new technique (HI-Z Turb'N Tag, U.S. Patent No. 4,970,988) for estimating turbine passage survival was applied to juvenile American shad (Alosa sapidissima) under three operating conditions at a hydroelectric project. Fish are fitted externally with the Turb'N tag and introduced into turbine penstocks. The Turb'N Tag inflates after turbine passage and buoys fish to the surface for recapture and examination; after removal of tags, fish are held to assess long-term effects. Almost all (96%) test (299) and control (300) fish were recovered; average recovery time was less than 9 min. The overall short-term (1 h) survival of test fish, adjusted for control, was 97%; 24- and 48-h survivals were 98 and 94%, respectively. The 48-h survival of test fish was 98–100% for mixed flow and Kaplan turbines and 66.8% for the mixed flow unit in the vented mode. Acute control mortality was negligible (< 5%). Our technique offers several significant advantages over traditional net recapture methods: applicable to wide range of species and size; allows predetermination of statistically valid sample size, level of significance, and power of the test to determine need for mitigation measures; and estimation of cumulative effects of multiple turbine exposure.

The hypotheses that fish survival probabilities may be lower (1) at less than peak operating turbine efficiency; (2) at deeper entrainment depth; and (3) with the deployment of extended‐length intake guidance screens, are not supported by results on yearling chinook salmon smolts (Oncorhynchus tshawytscha) at Lower Granite Dam, Snake River, Washington. Estimated 96 h survival probabilities for the six test conditions ranged from 0.937 to 0.972, with the highest survival at turbine operating towards the lower end of its efficiency. A blanket recommendation to operate all Kaplan type turbines within ± 1 percent of their peak efficiency appears too restrictive. Cavitation mode survival (0.946) was comparable to that at peak operating efficiency mode (0.937), as was the survival between upper (0.947) and mid depths (0.937). Survival differed only slightly among three turbine intake bays at the same depth (0.937 to 0.954), most likely due to differential flow distribution. Extended‐length intake fish guidance screens did not reduce survival. However, the sources of injury somewhat differed with depth; probable pressure and shear‐related injuries were common on fish entrained at mid‐depth, and mechanically‐induced injuries were common at upper depth. Operating conditions that reduce turbulence within the turbine environment may enhance fish survival; however, controlled experiments that integrate turbine flow physics and geometry and the path entrained fish traverse are needed to develop specific guidance to further enhance fish passage survival.

We conducted field studies and laboratory experiments to explore the relationship between direct injury and mortality rates of juvenile Pacific salmon Oncorhyncus spp. and the jet entry velocities characteristic of high-flow (Ͼ28.3 m 3 /s) outfalls at hydroelectric facilities. During field tests, the range of calculated mean entry velocities was 9.3-13.7 m/s for low (28.3 m 3 /s) and high (68.0-70.2 m 3 /s) outfall discharge rates and two receiving water elevations. Mortality and injury rates of balloon-tagged hatchery juvenile spring chinook salmon O. tshawytscha in the field tests were less than 1%. At a high-velocity flume in a laboratory, small (87-100 mm fork length [FL]) and large (135-150 mm FL) hatchery fall chinook salmon were exposed to velocities of 0.0-24.4 m/s in a fast-fish-to-slow-water scenario. Jet entry velocities up to 15.2 m/s provided benign passage conditions for the sizes and physiological states of juvenile salmonids tested under the particular environmental conditions present during this study. Our results of direct injury and mortality indicate that a jet entry velocity up to 15.2 m/s should safely pass juvenile salmon at high-flow outfalls. It will be necessary, however, to conduct site-specific, postconstruction verification studies of fish injury and mortality at new high-flow outfalls.

The immediate (1-h) turbine-related mortality of juvenile American shad Alosa sapidissitna at the Hadley Falls Hydroelectric Station on the Connecticut River, Holyoke, Massachusetts, was estimated to be 0% ± 14.5% (95% confidence interval) at the 35% wicket gate opening and 2.7% ± 16.2% at the 100% opening. We used the HI-Z TurtV N tag-recapture technique, which helped minimi/e control mortality and maximize recapture rates. Earlier literature estimates of turbine-related mortality (up to 82%) of juvenile alosids in passage through Kaplan turbines, in our view, were substantially overstated due to either low recapture rate, high control mortality, or both.