To help young salmon survive their perilous migration through the Sacramento–San Joaquin River Delta, the Department of Water Resources (DWR) has begun installing a bioacoustic fish fence at the junction of the Sacramento River and Georgiana Slough. Once fully installed, the fence will help sensitive fish species safely traverse through the Delta, including winter-run and spring-run Chinook salmon.
Bioacoustics is a cross-disciplinary science that combines biology and acoustics in the investigation of sound production, dispersion, and reception in animals. The fence uses a combination of bubbles, light, and sound to discourage migrating salmon from entering Georgiana Slough where their chances of survival decrease. As they travel downstream through the Delta, they disperse among its complex network of channels where they are subject to a variety of conditions that affect their rate of migration; vulnerability to predation; feeding success; growth rates; and ultimately, survival.
Chinook salmon are listed as endangered under the California Endangered Species Act and the U.S. Endangered Species Act. Studies have shown that salmon that leave the main stem of the Sacramento River and move into the interior and south Delta via alternative routes, including the Delta Cross Channel and Georgiana Slough, experience greater losses through encounters with predators. Seasonal closure of the Delta Cross Channel gates provides a degree of protection for migrating salmon during the Spring-run months between February and May. The bioacoustic fish fence will do the same but with the added advantage that it will not obstruct boat traffic or flows into Georgiana Slough where unimpeded flow is essential to maintaining water quality in the interior Delta.
“Acoustic and light-based behavioral systems have proven to be more effective than physical screens in cases where waterways need to remain navigable, and when fish need to be diverted from places where they might be at risk,” said Shahid Anwar, DWR senior engineer and project lead. “As fish protection needs and regulations evolve, so too have systems like the bio-acoustic fish fence that we’re installing at Georgiana Slough.”
Fish Guidance Systems, the UK-based company manufacturing the bioacoustic fish fence, is a leading designer of sound and light-based fish deterrence systems around the world and has partnered with DWR on the Georgiana Slough Migratory Salmon Barrier Project.
Installation of the fence was originally scheduled for earlier this year but high flows in the Sacramento River following last winter’s record-setting snow and rainfall prevented divers from installing the underwater structures in the river’s turbid water.
“We’ve had to wait until the river calms down before starting in-water work. Poor visibility in the water makes it a challenging work environment even at the best of times. High flows like those we’ve seen this spring make it hazardous for our divers,” said David Lambert, Fish Guidance Systems managing director.
Installation and operation of the fence is currently planned for eight years starting in late 2023 through 2030. Components will be reinstalled each February and removed in May, leaving in place the pilings to which they are attached. The pilings present no obstacle to commercial or recreational boat traffic. Although the flashing lights and bubbles can be seen from above the water, virtually none of the sound is audible above the surface.
DWR will conduct monitoring to assess the performance of the barrier, which will include the use of fish tracking and other data collection monitoring equipment.