Rotary Screw Traps Are Coming To The North Yuba!

Rotary Screw Traps (RST) are specially designed sampling devices used to capture downstream migrating juvenile fish such as salmon and steelhead. They are large, cylindrical traps that float on pontoons. This October, two RSTs will be installed on the North Yuba River, one at Rocky Rest Campground at RM 25.6 and the other along Old Toll Bridge Road at RM 33.6. They will be there from October 2023 to May 2024. Public outreach events regarding these RSTs will be held at the end of August in both Downieville and in Nevada City. These RSTs will eventually be trapping fish and gathering data for the Yuba Salmon Study, a project of NOAA and CDFW. 

While they are important data gathering devices, RSTs can be dangerous to you and your loved ones—including your pets. You can easily enter the mouth of the rotating cone, become injured by the rotating wings, and even possibly get pinned underwater. With two of these devices going into the North Yuba River, it is important that you are aware of these dangers. Never swim or float near an RST and make sure your pets don’t go near them either. Do not climb on an RST, as this is dangerous and could possibly damage the RST.  

The Yuba Salmon Study is a collaborative planning and implementation program led by National Oceanic and Atmospheric Administration (NOAA) Fisheries and California Department of Fish & Wildlife (CDFW). The vision of this project is to reintroduce spring-run Chinook salmon to their historical habitat in the upper Yuba River watershed through a phased, science-based, and cost-effective reintroduction project that will inform future Central Valley reintroduction decisions.  

The RSTs going into the North Yuba consist of three main components: a 5-foot or 8-foot diameter cone, a trap box, and pontoons. Inside of the cone, wings are situated in a spiral shape so that, as stream currents push against them, the cone will rotate on its horizontal axis much like a windmill. As downstream-moving fish enter the mouth of the rotating cone, they are guided to a submerged trap box where the fish are held until they are sampled and then released. The pontoons provide floatation for the cone and trap box assembly.   

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The two RSTs will be installed on the North Yuba River, one at Rocky Rest Campground at RM 25.6 and the other along Old Toll Bridge Road at RM 33.6 from October 2023 to May 2024. 

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Rocky Rest Campground is located off of Hwy 49 near Downieville. At this site, the RST will be anchored to a cable elevated well above the water surface and suspended between two large trees upstream of the walking bridge. The RST will be tethered to that cable using two “leader” cables. In this way operators will be able to be adjust the trap upstream and downstream with discharge to maximize its trapping efficiency, or readily move it out of the main current in the event of high water. 

The RST off of Old Toll Bridge Road will be located approximately 0.5 miles upstream of the intersection of Mountain House Rd and Old Toll Bridge Road, upstream of the community of Goodyears Bar. At this site, the RST will be installed using one cable running upstream, at water level, to a cluster of alders near a natural backwater feature. A second cable will be anchored directly to shore, keeping the RST close to the river-left bank. A single, lightweight cable will be run between two trees to suspend an in-water hazard sign.    

These RSTs will be running in the river from October 2023 to May 2024. Come learn more about this study and RSTs, get your questions answered, and meet some of the people behind this project at two public outreach events. 

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The Downieville Public Outreach Meeting will be held on August 23rd from 4:30 to 6:30 at Sabrina’s at the Forks (308 Main St, Downieville CA 95936).

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The Nevada City Public Outreach Meeting will be held on August 30th from 4:30-6:30 at the Gene Albaugh Community Room at the Nevada County Library (980 Helling Way, Nevada City, CA 95959).  

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