The following is a letter to the editor, published here as opinion. The opinions expressed in this letter are those of the writer. If you would like to submit a letter to the editor feel free to write to [email protected].
The Eel River Recovery Project has collected water temperature and flow data and documented the fish community in the Tenmile Creek watershed that surrounds Laytonville since 2018, and this is an announcement of the release of their Water Year (WY) 2022 findings. Starting on October 1, 2021 and extending to September 30, 2022, it was a year of extremes. Although rainfall was only 70% of normal, conditions were dramatically better for fish than in WY 2021, when most Tenmile Creek reaches and tributaries went completely dry.
An atmospheric river on October 24, 2021 caused record flows for the date in the South Fork Eel River, and kicked the water year off with a bang. Timely rains continued through early January 2022, allowing excellent access for Chinook and coho salmon spawning. Then rain ceased from January through March, setting another record for lowest rainfall for those three months in California history, and preventing adult steelhead from reaching headwater spawning grounds.
By early April stream flows were at record lows, then unusual mid-April rains helped expand habitat and maintain connected flow in some Tenmile Creek reaches and tributaries in summer.
Juvenile salmonid surveys from May through October had some real surprises. Young of the year trout were present at many locations, despite lack of access for steelhead spawning, which indicates that native trout spawning is contributing to the population. Steelhead and rainbow trout are the same species and any individual fish may manifest a resident or anadromous life history.
By far the greatest surprise was the abundance of coho salmon juveniles in upper Cahto Creek, Mill Creek and lower Little Case Creek in September. Coho had only been documented once by ERRP in 2018, when they were found in Big Rock Creek. Chinook salmon usually migrate to the estuary immediately upon emergence from the gravel, but many were found rearing in Streeter and Tenmile creeks in May 2022, and juveniles were lingering in lower Cahto Creek into July 2022. This suggests production of a very large year-class. However, poor ocean conditions may have limited their survival, as indicated by a modest fall 2022 return of jack salmon, small male Chinook that return to spawn after less than one year in the ocean.
Thomas Gast Associates Environmental Consulting measured WY 2022 flows at six locations in the Tenmile Creek watershed. Many of their sites lost connecting flow in August, except lower Tenmile Creek not far upstream of the SF Eel River and Mill Creek. Mill Creek and lower Little Case Creek lost surface flow only briefly in early September during a severe heat wave, but pools remained supportive of coho juveniles. Within days, the flow reconnected as a result of a trace of rain and cooler nights. The latter triggered reduced tree evapotranspiration in the watershed, reviving flows and insuring coho survival.
The mainstem reach at Tenmile Creek Road had connected flow and supported steelhead as did isolated stratified pools in lower Cahto Creek, upper Streeter Creek, and Tenmile Creek above and below Peterson Creek. ERRP has identified lower Tenmile Creek tributary Peterson Creek, as a critical refugia for steelhead rearing and also for all salmonid juveniles from throughout the watershed. The cold-water plume at the mouth provides an island of cold-water habitat for migrating salmon and steelhead young, as lower Tenmile Creek rises to stressful or lethal temperatures.
The flow increase in response to reduced evapotranspiration in mid-September offers hope that ERRP planned forest thinning projects will help improve critical baseflows, including in Peterson Creek. We are also exploring community interest in acquiring funding for augmented storage in the Cahto, Mill and Little Case Creek watersheds. This would enable residents to forbear from dry season water extraction, as another way of increasing flows for fish.
Funding for Tenmile Creek monitoring comes from the State Water Resources Control Board (#D2013114) and the State Coastal Conservancy (# 20-076). ERRP Managing Director Pat Higgins said, “We really appreciate the SWRCB and SCC for supporting monitoring that helps us keep people informed about the health of their creek and watershed. Every year the data has something else to teach us.”
The full report is entitled Tenmile Creek Water Temperature, Fish Community and Flow Summary Report: Water Year 2022 and is available online at www.eelriverrecovery.org. It has links to fish videos so that readers reviewing the document can see movies of the fish at various monitoring locations, and flow movies made up of timelapse camera photos from eight sites in the Tenmile Creek watershed. Call 707 223-7200, if you have questions or want to get involved in monitoring.