In 2019 and 2020, FISHBIO was hired to install an anti-spawning mat in the Sacramento River to prevent endangered winter-run Chinook salmon from laying eggs in an area that would be disturbed by construction of a new bridge at Jelly’s Ferry near Red Bluff, California. The anti-spawning mat consisted of chain-link fence that covered an area of nearly 3,500 square feet along the river bottom. The mat was secured to the substrate using earth anchors and steel pins, which had to be pounded into the substrate using a hydraulic jack hammer. Once secured in place, steel cable was woven between the different sections of fencing for added strength.
Securing the mat was made all the more complicated by the high flows experienced in 2019, which necessitated the use of scuba gear to install the mat in depths of water greater than six feet in some areas. The added reinforcement was necessary to keep in the mat in place during times of the year when flows in the Sacramento can reach as high as 119,000 cfs, as they did on April 1, 1974. Although flows did not reach nearly that high in 2019 and 2020, the anti-spawning mat performed admirably and remained firmly in place while it was installed from May–November in 2019 and March–November in 2020.
Although the Jelly’s Ferry Road bridge is located downstream of the majority of winter-run spawning habitat in the Sacramento River, any redds dug in the area could have been affected by siltation, construction debris, load noises, and contaminants associated with construction activities. This mat it intended to encourage salmon spawning in more suitable habitat upstream during bridge construction.