9781934874264-ch15

Telemetry Techniques: A User Guide for Fisheries Research

Section 8.1: Use of Acoustic Telemetry to Evaluate Survival and Behavior of Juvenile Salmonids at Hydroelectric Dams: a Case Study from Rocky Reach Dam, Columbia River, USA

Tracey Steig and Christopher Holbrook

doi: https://doi.org/10.47886/9781934874264.ch15

Columbia and Snake river salmon and steelhead Oncorhynchus spp. populations have declined from historic levels due to several factors, including the operation of hydroelectric dams. While most downstream migrating juvenile salmon and steelhead pass safely through a single dam, cumulative mortality through several dams can be significant (Davidson 1965; Bell et al. 1967; Schweibert 1977). Mortality during dam passage is generally attributed to turbine entrainment or deep spillway passage, sometimes in combination with tailrace predation. Since the early 1980s, considerable effort has been devoted to the development of structures and project operations that safely bypass downstream migrants around dams. However, the success of a bypass structure depends on survival advantage through the bypass compared to other routes, and the fraction of the population that uses each route. Rigorous evaluations are needed to determine the effectiveness of fish passage improvements. This Section will review a case study describing the use of acoustic telemetry to evaluate fish passage at Rocky Reach Dam on the mid-Columbia River.

Simple methods can be used to estimate survival of a fish population as it passes a dam, however more complex approaches are required to show sources and mechanisms of mortality. At the simplest level, survival in river reaches containing dams can be compared to other river reaches lacking dams (Skalski et al. 1998; Holbrook et al., in press), or dam survival can be estimated directly by comparing survival of fish released above and below dams (Burnham et al. 1987; Skalski et al. 2001). While these methods quantify the effect of a dam on a population, they do not reveal sources of mortality.