Juvenile rainbow trout Oncorhynchus mykiss and steelhead (anadromous rainbow trout), fall (age‐0 and age‐1) and spring Chinook salmon O. tshawytscha, and American shad Alosa sapidissima were exposed to shear environments in the laboratory to establish injury–mortality thresholds based on estimates of strain rate. Fish were exposed to a submerged jet having exit velocities of 0 to 21.3 m/s, providing estimated exposure strain rates up to 1,185/s. Turbulence intensity in the area of the jet where fish were subjected to shear was minimal, varying from 3% to 6% of the estimated exposure strain rate. Injuries and mortalities increased for all species of fish at strain rates greater than 495/s. American shad were the most susceptible to injury after being subjected headfirst to a shear environment, while steelhead and rainbow trout were the most resistant. There was no apparent size‐related trend in susceptibility to high shear except that age‐0 fall Chinook salmon were more resistant to shear environments than age‐1 fall Chinook salmon. All groups of test fish exposed headfirst to high‐shear environments had higher injury–mortality rates than fish introduced tailfirst at similar strain rates. These results document the relationship between fish injury and a fluid force present at hydroelectric facilities and provide biological specifications for improving fish passage and survival.

This study investigated the mortality of and injury to juvenile Chinook salmon Oncorhynchus tshawytscha exposed to simulated pressure changes associated with passage through a large Kaplan hydropower turbine. Mortality and injury varied depending on whether a fish was carrying a transmitter, the method of transmitter implantation, the depth of acclimation, and the size of the fish. Juvenile Chinook salmon implanted with radio transmitters were more likely than those without to die or sustain injuries during simulated turbine passage. Gastric transmitter implantation resulted in higher rates of injury and mortality than surgical implantation. Mortality and injury increased with increasing pressure of acclimation. Injuries were more common in subyearling fish than in yearling fish. Gas emboli in the gills and internal hemorrhaging were the major causes of mortality. Rupture of the swim bladder and emphysema in the fins were also common. This research makes clear that the exposure of juvenile Chinook salmon bearing radiotelemetry transmitters to simulated turbine pressures with a nadir of 8-19 kPa can result in barotrauma, leading to immediate or delayed mortality. The study also identified sublethal barotrauma injuries that may increase susceptibility to predation. These findings have significant implications for many studies that use telemetry devices to estimate the survival and behavior of juvenile salmon as they pass through large Kaplan turbines typical of those within the Columbia River hydropower system. Our results indicate that estimates of turbine passage survival for juvenile Chinook salmon obtained with radiotelemetry devices may be negatively biased.

A cross-sectional study of 178 asymptomatic contact lens wearers attending 10 contact lens practices in the west of Scotland was conducted over a 4 month period. The aims of the study were to identify specific microbial con- (BrJ Ophthalmol 1993; 77: 41-45)

Excess energy expenditure during the upstream migration of adult fall chinook salmon Oncorhynchus tshawytscha may reduce spawning success or lead to increased prespawning mortality. Recent advances in biotelemetry make it possible to assess the energetic costs of upstream migration. Our objectives were to evaluate the use of physiological telemetry to estimate the energy expended by adult fall chinook salmon at different swimming velocities and to compare these data to those associated with other species of salmonids. An electromyogram (EMG) telemetry system was used to obtain, transmit, and record an integrated EMG pulse signal that represented the time between muscle contractions. The EMG telemetry system provides a means to evaluate the effects of structural or operational changes in the hydropower system on energy expenditure and reproductive success of upstream migrant adult salmon. Seven adult salmon (71.5 to 106 cm fork length [FL]) were tagged and exercised in a respirometer at 15 and 20°C. The EMG pulse rates were similar between temperatures tested, but small fish (≤90 cm FL) had a greater pulse rate than did large fish (>90 cm FL). Oxygen consumption was related to swimming velocity, and approximately 76% of the variance in oxygen consumption could be explained by a model that included EMG pulse rate and fish size‐class designation. The results of our study showed that adult fall chinook salmon had similar swimming performances when compared with other salmonids, and EMG transmitters could be used to assess activity rates (and oxygen consumption) in wild migrating fall chinook salmon.

Fish screens associated with irrigation diversion structures perform a vital function by protecting rearing and migrating fishes. Irrigation diversions in the western United States were developed in the late 1800s and early 1900s with little regard to how they might affect fish populations. Fish screens were installed on some diversions beginning in the 1930s but were often ineffective. Beginning in the 1980s a “modern‐era” fish screening program was initiated in the Yakima River basin in Washington State. A systematic phased approach was employed, with federal funding, to replace antiquated screens and to install screens where there had not previously been fish protection devices. Also during this time, the federal and state agencies responsible for protecting the fish resources developed regional criteria to guide design of these facilities. These criteria, developed by the National Marine Fisheries Service and used by the Washington Department of Fish and Wildlife, dictated physical metrics such as approach velocity (and mesh size) for fish screen facilities. Scientists at the Pacific Northwest National Laboratory (PNNL) developed methods for evaluating new fish screen facilities as they came “on line” to document whether the facilities were designed, constructed, operated, and maintained to be within the fish passage criteria. PNNL uses a combination of water velocity measurements, visual inspection, and underwater videography to determine whether fish screen sites are within the fish protection criteria. This annual evaluation schedule (most sites are evaluated three times/year) is a vital tool to ensure that the large initial capital investment (over $75 million USD) is being operated and maintained to protect fish.