We developed a rapid method for detecting and quantifying the pathogen Renibacterium salmoninarum in coelomic fluid of spring chinook salmon (Oncorhynchus tshawytscha) by concentrating the bacteria on 0.2-μm polycarbonate filters and staining them with specific fluorescein-labeled antibody. Centrifugation of samples and resuspension of the sedimented material in phosphate-buffered saline containing Triton X-100 increased the ease of filtration. Background fluorescence was reduced by counterstaining filters with Eriochrome black T. Postfiltration staining, rinsing, and counterstaining were done in the syringe-mounted filter holders, reducing handling of the filters and possible loss of bacteria. The number of bacteria detected by the filtration – fluorescent antibody technique in a broth culture of R. salmoninarum ranged from 6.7 × 107to7.6 × 107/mL and was slightly higher than that determined by plate count (9.6 × 106/mL). Increasing the sample dilution or decreasing the number of microscope fields examined generally increased the variability of filter counts of R. salmoninarum. Using the filtration – fluorescent antibody technique, we detected the bacterium in the coelomic fluid of 85% of spawning female spring chinook salmon sampled from a hatchery population.

In spring 1996 and 1997, we studied the prototype surface bypass and collector (SBC) at Lower Granite Dam on the Snake River in Washington. Our objectives were to determine the most efficient SBC configuration and to describe smolt movements and swimming behavior in the forebay. To do this, we used hydroacoustic and radiotelemetry techniques. The SBC was retrofitted onto the upstream face of the north half of the powerhouse to test the surface bypass method of diverting smolts from turbines. The SBC had three entrances, with mean velocities ranging from 0.37 to 1.92 m/s, and it discharged 113 m 3 /s through its outlet at Spill Bay 1, which was adjacent to the powerhouse. Different SBC configurations were created by altering the size and shape of entrances. During spring 1996 and 1997, river discharge was well above normal (123 and 154% of average, respectively). Powerhouse operations caused a strong downward component of flow upstream of the SBC. Many smolts (primarily steelhead and secondarily chinook salmon) were observed actively swimming upward in the water column. There were four times as many smolts diverted from turbines per unit volume of water with SBC flow than with spill flow, which indicated that the SBC may be an especially important bypass consideration in moderate-or low-flow years. The highest SBC efficiency (the proportion of total fish passing through the north half of the powerhouse by all routes that passed through the SBC) for any configuration tested was about 40%. Although no single SBC configuration stood out as the most efficient, the horizontal surface and maximum area configurations, or some combination of the two, are worth further investigation because they were moderately efficient.

Several hydroelectric dams in the Snake-Columbia river system are equipped with submersible traveling screens that project into the turbine intakes. The screens are designed to divert juvenile migrant Pacific salmon Oncorhynchus spp. and steelhead Salmo gairdneri from the intake upward into gatewells and the ajoining central bypass system. Assays of gill Na+,K*-ATPase were performed on yearling chinook salmon O. tshawytscha collected during several routine fish guidance efficiency tests in 1985 and 1986. On three of the four sampling dates, gill Na*,K 4 -ATPase levels were significantly higher in fish guided into the gatewell than in those not guided. These data suggest there is a relationship between the physiological status of smelting yearling chinook salmon and their susceptibility to guidance by traveling screens. Assessments of salmonid out-migrations may be biased if they are based on samples from traveling-screen guidance systems.

Materials and methodsAcute temperature preference tests were conducted with American eels, Anguilla rostrata. collected from Maryland's eastern shore. Eels were acclimated to temperatures of 6, 12, 18, 24 and 30°C. Final temperature preferendum was 16.7°C. Data differ from the temperature responses of the majority of fishes tested to date in that acclimation temperature did not influence selected temperatures. Similar results were obtained for various other fishes (Oncorhynchus, Salmo, Salvelinus) by other investigators.Behavioral responses at various acclimation temperatures were observed.

Consistent relationships among certain physical parameters with stream order have been shown (summarized in Platt 1974). These parameters in combination are significant in influencing fish population densities and species diversity. Diversity of fishes in Raystown Branch was correlated most highly with stream order; other physical data were significantly correlated with both diversity and stream order. Data from Raystown Branch support the hypothesis that stream order represents a multidimensional network of the physical parameters which comprise it and, as such, can be used as a satisfactory composite index.