Monday August 1, 2022
Redhead Blackbelt —
The seventh annual Eel River Recovery Project pikeminnow survey of a key reach of the South Fork Eel River took place on June 28 and 29 and the population of this non-native predator remains high. However, there were a surprising number of salmon and steelhead juveniles and signs of ecological resilience. Once again, the University of California, Berkeley dive team proved strategic partners, including post-doctoral researcher Phil Georgakakos and undergraduates Michael Schweiker and Stella Stein.
The two-day survey extends from the Hermitage at the mouth of Rattlesnake Creek to Standish Hickey State Park. The mid-point of the survey is Cedar Creek at the Gomde Monastery, where the first day’s dive ends the second leg of the survey starts. Divers form a line as they swim through runs and pools and count as a team. Only pikeminnow over four inches in length are counted, with fish of different sizes recorded: 4-8”, 8-12”, 12-16”, and greater than 16 inches. The larger the fish, the more native fish juveniles, including salmon and steelhead it consumes. The total number of pikeminnow over four inches in 2022 was 3867, which is down from the previous two years when there were 6639 in 2020 and 4075 in 2021. However, the first four years of the survey found an average of 1094 pikeminnow and the drought of 2020 and 2021 allowed the population to increase. One quarter of the pikeminnow were over 8”, and many will grow to greater than 16” in the next few years, leading to greater predation pressure on native fish.
The most surprising part of the dive was the number of juvenile steelhead, with several age classes and fish up to ten inches long, which could also be native rainbow trout. Because of high flows this year, divers could swim much of the way, knocking insects off rocks while navigating plunging waters. This created a feeding frenzy, and coming out of the bubbles, divers saw schools of panicked trout within inches of their masks. Similar to early 2022 surveys, juvenile Chinook were numerous and seen along the entire survey route, and even incidental coho salmon were observed.