Limitations of biotelemetry technology available in 2001 prompted the U.S. Army Corps of Engineers Portland District to develop a new acoustic telemetry system to monitor survival of juvenile salmonids through the Columbia River to the Pacific Ocean. Eight years later, the Juvenile Salmon Acoustic Telemetry System (JSATS) consists of microacoustic transmitters (12 mm long, 0.43 g weight in air), autonomous and cabled receiving systems, and data management and processing applications. Transmitter pulse rate can be user‐defined and as configured for this case study was set at 5 seconds, with an estimated tag life of 30 days and detection range of 300 m. Before JSATS development, no technology existed to study movement and survival of fish smaller than 10 g migrating long distances from freshwater and into saltwater. In a 2008 study comparing detection probabilities, travel times, and survival of 4,140 JSATS‐tagged and 48,433 passive integrated transponder (PIT)‐tagged yearling Chinook salmon (Oncorhynchus tshawytscha; mean fork length 133.9 and 135.3 mm, for JSATS and PIT‐tagged fish, respectively) migrating the Snake and Columbia rivers to the Pacific, the JSATS provided survival estimates at more locations with greater precision, using less than one‐tenth as many tagged fish as the traditional PIT‐tag system. While designed to be optimized for juvenile salmonid survival assessment in the Columbia River basin, JSATS technology may be used in a variety of environments. Information regarding different acoustic telemetry systems from various vendors is presented and discussed relative to the nonproprietary JSATS.

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Low‐ and high‐frequency sounds were tested as a means of repelling blueback herring Alosa aestivalis in confined‐area and open‐water experiments. Confined‐area tests were performed by analyzing the response of blueback herring in floating net‐pens to sounds differing in frequency, sound pressure levels (SPLs, given in decibels [dB] in reference to l.0 μPa), and pulse width. Highfrequency sounds between 110 and 140 kHz, at SPLs above 180 dB (at 1.0 m from the transducer) and at various pulse widths, elicited statistically significant (P < 0.05) avoidance responses by blueback herring. A reduced response was observed at sound frequencies of 100 and 150 kHz. Low‐frequency sounds between 0.1 and 1 kHz at SPLs of 160–175 dB (at 1.0 m from the transducer) elicited only short‐term startle responses. Field tests were performed at Richard B. Russell Dam (on the Savannah River at the Georgia‐South Carolina border) to evaluate candidate transducers and amplifiers. In field evaluations a single high‐frequency transducer emitting 124.6‐ and 130.9‐kHz sounds at an SPL of 187 or 200 dB (at 1.0 m) partially repelled blueback herring that were approximately 60 m away from the transducer for periods of up to I h. These results suggest that high‐frequency sound may provide an effective and inexpensive method, relative to structural measures, for reducing entrainment of blueback herring at hydropower stations.

The combined model produced a tool for evaluating effects on fish populations from passage through hydropower turbines at dams. Mean blade-strike mortality was higher for adult Atlantic salmon ( Salmo salar ) and sea-run brown trout ( Salmo trutta ) (25.2%–45.3%) than for juveniles (5.3%–9.7%). Based on life cycle modeling, salmon populations in two Swedish rivers responded differently to strategies for mitigating mortality caused by fish striking turbine blades. Although population growth rates increased up to 3% and were relatively similar for both rivers, the relative increase in the number of female salmon escaping above a dam annually after 20 years when both juveniles and adults were protected was greater in the River Piteälven (68%) than in the River Vindelälven (46%) and was approximately four times greater in the River Piteälven (38% vs. 10%) when only adults were protected. These population responses were not predicted by estimates of mortality through turbines. They showed the model could be used to evaluate strategies to conserve fish populations affected by dams located in fish migratory corridors and how postspawn adults contributed to population productivity.