75th Celebration: 1957 - Keeping Fish in the River

When settlers first diverted water from streams and rivers into their fields, they likely diverted more than water. Fish following the flow of water, especially downstream migrating salmon smolts, were often carried out of a stream, into irrigation canals and onto farmers' fields. As early as 1905, fish screens were being promoted as a way to keep fish in the streams and out of irrigation canals. Screening irrigation diversions is more complicated than it sounds. The engineering is often specific to each location and screens require ongoing maintenance, repair and cleaning. Efforts to install a successful long-term fish screen are often defeated by the lack of associated maintenance due to river bedload and debris. Dramatic declines of Idaho's anadromous salmon and steelhead runs pushed designs and funding for fish screens on rivers with anadromous fish into high gear. In 1938 the U.S. Congress passed the Mitchell Act in an attempt to partially mitigate for fish and wildlife losses from hydroelectric projects, logging, mining and agricultural developments. The Act provided a program for conserving anadromous fisheries of the Columbia Basin. In 1956, the program was extended to include the upper Salmon River basin, which led to Idaho Fish and Game's Fish Screen Program being established in 1957. Idaho Fish and Game estimated that historically the Salmon River basin produced 39% of the spring Chinook salmon and 45% of the summer Chinook salmon in the Columbia River system. The upper Salmon River and its tributaries provided much of this spawning and rearing habitat. Numerous studies have shown that juvenile salmon compose the majority of fish lost to irrigation diversions in the upper Salmon River basin. In 1958, it was estimated that 423,000 salmon fingerlings were lost in 90 irrigation canals in the Lemhi River alone. Between 1958 and 1966, the Fish Screen Program constructed more than 250 screens on the main stem Salmon River and tributaries such as the Lemhi River. To read more of this story and other 75th Celebration articles, go to https://fishandgame.idaho.gov/75th.