Salmonid Field Protocols Handbook: Techniques for Assessing Status and Trends in Salmon and Trout

Fish Counting at Large Hydroelectric Projects

Paul G. Wagner

doi: https://doi.org/10.47886/9781888569926.ch11

In the Pacific Northwest, salmon and steelhead Oncorhynchus mykiss are an integral part of tribal and nontribal cultures, supporting important subsistence, commercial, and recreational fisheries. During the past century, salmon stocks have declined on the U.S. Pacific Coast to the point where several populations are now listed as threatened or endangered under the Endangered Species Act. The reasons for the decline are many, including extensive development of hydroelectric projects. Because salmon and steelhead are such an important part of the Pacific Northwest economy, culture, and heritage, widespread salmon recovery efforts are currently underway. Accurate juvenile and adult passage estimates at large hydroelectric projects can be vital to monitoring the success or failure of these efforts and are also frequently used for a variety of other management applications.

Hydroelectric projects can impede anadromous salmonid passage at adult and juvenile life stages. Where possible, passage facilities such as adult fishways and juvenile (smolt) bypass systems are often included in hydroelectric project design or retrofitted to older existing structures. Juvenile bypass systems are intended to divert downstream migrating smolts away from turbine intakes through screening, louver, gulper, or surface collection systems. At large hydroelectric projects, these juvenile bypass systems often include collection facilities where fish may be held and counted, anesthetized and examined, used in research studies, or loaded into vehicles such as tanker trucks or barges to be transported downstream around other hydroelectric projects. Adult passage facilities are typically of pool and weir design and are intended to attract and provide safe passage for adult upstream migrants. Such facilities are usually equipped with count stations that allow enumeration of migrants by either direct observation or interrogation of time-lapse video. In addition, adult fishways often include a trap so that fish can be sampled, marked, or loaded into tanker trucks for transport upstream around other existing nonpassable hydroelectric projects to otherwise inaccessible spawning habitat.

The Columbia River basin has been called the most hydroelectrically developed river system in the world. Large hydroelectric project development began with the completion of Rock Island Dam in 1932, followed by much larger federal projects such as the Bonneville and Grand Coulee dams completed in 1938 and 1941, respectively (see the Center for Columbia River History Web site, <www.ccrh.org/river/history.htm#hydro>). Eleven large hydroelectric projects currently exist in the U.S. portion of the mainstem Columbia River; numerous other projects occupy the tributaries.