Surface bypass as a means to protect downstream-migrating fish – lack of standardized evaluation criteria complicates evaluation of efficacy

Surface bypasses are downstream migration structures that can help reduce hydropower-induced damage to migrating fish. However, no comprehensive design concept that facilitates good surface bypass performance for a wide range of sites and species is available. This is why even efficiencies at recently built bypass structures vary widely between 0% and up to 97%. We reviewed surface performance studies and existing guidelines for salmonids, eels, and potamodromous species if available to identify crucial design criteria for surface bypasses. Two-tailed Pearson correlation of bypass efficiency and bypass design criteria shows that bypass entrance area (R=0.3300, p=0.0036) as well as proportion of inflow to the bypass (R=0.3741, p=0.0032) are the most influential parameters on bypass efficiency. However, other parameters like guiding structures and trash rack spacing though not statistically significant (Spearman correlation, ordinary t-test) have shown to have an effect on efficiency in some studies. The use of different performance criteria and efficiency definitions for bypass evaluation hampers direct comparison of studies and therefore deduction of design criteria. To enable meta-analyses and improve bypass design considerations we suggest a list of standardized performance parameters for bypasses that should be followed in future bypass performance studies

Feasibility of tracking fish with acoustic transmitters in the Ice Harbor Dam tailrace

The Juvenile Salmon Acoustic Telemetry System (JSATS) has been used at many dams but has never been deployed in the near-dam tailrace environment. The use of JSATS in the tailrace is of interest to fishery managers to evaluate downstream passage behavior of juvenile salmonids and dam approach behavior of upstream migrating adult salmon and lamprey. The acoustic noise level and detection range of JSATS were studied to determine the feasibility of deploying JSATS in the Ice Harbor Dam tailrace. The noise level measured from the powerhouse deck was less than 104 dB re 1 mPa except for the turbine outlet near the spillway, and 350 mdownstream of the dam, the noise level was less than 106 dB. The measured noise levels would allow a theoretical detection range of 100 m to 350 m and 85 m to 320 m, respectively. Validation experiments showed that the detection range is 113 to 184 m using hydrophones deployed from the powerhouse deck and 148 m using hydrophones deployed 500 m downstream of the dam

Improving Hydroturbine Pressures to Enhance Salmon Passage Survival and Recovery

Barotrauma caused by rapid decompression during hydroturbine (turbine) passage may occur as fish move through the low pressure region below the turbine runner. This scenario is of particular concern in North American rivers with populations of ESA-listed salmon. The US Army Corps of Engineers (USACE) and the Pacific Northwest National Laboratory released Sensor Fish into lower Snake and Columbia River turbines to determine the magnitude and rate of pressure change fish might experience. Recorded pressures were applied to simulated turbine passage (STP) in laboratory studies to determine the effect of rapid decompression on juvenile Chinook salmon. These STP studies have increased our understanding of how pressure effects fish passing through turbines and suggest that the ratio of pressure change (acclimation pressure [the depth upstream of the dam where fish are neutrally buoyant] divided by nadir pressure [lowest pressure]) is highly predictive in determining the effect on smolt survival. However, uncertainty remains in smolt acclimation depth prior to entering turbine intakes at hydroelectric facilities. The USACE continues to make progress on salmon survival and recovery efforts through continued research and by applying pressure study results to turbine design. Designing new turbines with higher nadir pressure criteria is likely to provide safer fish passage for all salmonid species experiencing turbine passage

Sensitivity and Vulnerability of Brook Trout Populations to Climate Change

Predicting future brook trout Salvelinus fontinalis distributions at the population scale under various climate scenarios is of interest to the Eastern Brook Trout Joint Venture. Previous larger scale models have been useful in highlighting the potential threat; however, the predicted air and water temperature errors associated with these models makes predictions of the persistence of individual brook trout populations problematic. We directly measured paired air and water temperatures in watersheds (N = 77) containing reproducing populations of brook trout in Virginia. We found that paired air and water temperature relationships are highly variable among patches but are a useful dataset to classify sensitivity and vulnerability of existing brook trout patches. We developed a classification system using sensitivity and vulnerability metrics that classified sampled brook trout habitats into four categories (High Sensitivity- High Vulnerability (51.9%); High Sensitivity-Low Vulnerability (10.4%); Low Sensitivity-High Vulnerability (7.8%); Low Sensitivity-Low Vulnerability (29.9%). Our direct measurement approach identified potential refugia for brook trout at lower elevations and with higher air temperatures than previous larger scale modeling efforts. Our sensitivity and vulnerability groupings should be useful for managers making investment decisions in protecting and restoring brook trout

Three-dimensional migration behavior of juvenile salmonids in reservoirs and near dams

Abstract To acquire 3-D tracking data on juvenile salmonids, Juvenile Salmon Acoustic Telemetry System (JSATS) cabled hydrophone arrays were deployed in the forebays of two dams on the Snake River and at a mid-reach reservoir between the dams. The depth distributions of fish were estimated by statistical analyses performed on large 3-D tracking data sets from ~33,500 individual acoustic tagged yearling and subyearling Chinook salmon and juvenile steelhead at the two dams in 2012 and subyearling Chinook salmon at the two dams and the mid-reach reservoir in 2013. This research investigated the correlation between vertical migration behavior and passage routes. The depth distributions of fish within the forebays of the dams were significantly different from fish passing the mid-reach reservoir. Fish residing deeper in the forebay tended to pass the dam using deeper powerhouse routes. This difference in depth distributions indicated that the depth distribution of fish at the mid-reach reservoir was not related to behaviors of fish passing through certain routes of the adjacent dams. For fish that were detected deeper than 17.5 m in the forebays, the probability of powerhouse passage (i.e., turbine) increased significantly. Another important finding was the variation in depth distributions during dam passage associated with the diel period, especially the crepuscular periods

A field evaluation of an external and neutrally buoyant acoustic transmitter for juvenile salmon: implications for estimating hydroturbine passage survival

Turbine-passed fish are exposed to rapid decreases in pressure which can cause barotrauma. The presence of an implanted telemetry tag increases the likelihood of injury or death from exposure to pressure changes, thus potentially biasing studies evaluating survival of turbine-passed fish. Therefore, a neutrally buoyant externally attached tag was developed to eliminate this bias in turbine passage studies. This new tag was designed not to add excess mass in water or take up space in the coelom, having an effective tag burden of zero with the goal of reducing pressure related biases to turbine survival studies. To determine if this new tag affects fish performance or susceptibility to predation, it was evaluated in the field relative to internally implanted acoustic transmitters (JSATS; Juvenile Salmon Acoustic Telemetry System) used widely for survival studies of juvenile salmonids. Survival and travel time through the study reach was compared between fish with either tag type in an area of high predation in the Snake and Columbia rivers, Washington. An additional group of fish affixed with neutrally-buoyant dummy external tags were implanted with passive integrated transponder (PIT) tags and recovered further downstream to assess external tag retention and injury. There were no significant differences in survival to the first detection site, 12 river kilometers (rkm) downstream of release. Travel times were also similar between groups. Conversely, externally-tagged fish had reduced survival (or elevated tag loss) to the second detection site, 65 rkm downstream. In addition, the retention study revealed that tag loss was first observed in fish recaptured approximately 9 days after release. Results suggest that this new tag may be viable for short term (\u3c8 days) single-dam turbine-passage studies and under these situations, may alleviate the turbine passage-related bias encountered when using internal tags, however further research is needed to confirm this