Unraveling the mysteries of the Atascadero Creek watershed
By Sarah Nossaman Pierce
Nestled up against a verdant, forested ridge in western Sebastopol lies an idyllic little stream with plenty of cold, clear water and shady pools that look like prime fish habitat.
Redwood Creek is a tributary to Jonive Creek, which weaves under and along Bodega Highway before entering Atascadero Creek at the northwest corner of Ragle Ranch Park. Atascadero Creek then flows through Graton into Green Valley Creek, which meets the Russian River in Forestville.
Green Valley Creek is renowned as a critical and productive stronghold for endangered coho salmon and was the last stream in the Russian River watershed to support three consecutive year classes of coho (representing all year classes, given that coho have a three-year life cycle).
For decades, it has been a focal point of local salmon recovery efforts, but comparably little is known about the potential of Atascadero Creek and its tributary streams to support salmon.
Though the Atascadero sub-watershed comprises a full 60% of the Green Valley Creek watershed, it remains somewhat of a mystery to local biologists and natural resource managers.
The primary challenge is access to the stream channel. Atascadero comes from the Spanish verb "atascar"—meaning to get bogged down—and the name is no accident.
Between the cool, perennial waters of the upper watershed and Green Valley Creek lies the boggy, entangled, braided wetland complex of lower Atascadero. While the Atascadero marsh is designated as critical habitat and is teeming with sensitive plant and animal species, the physical complexity of the system makes accurately documenting water quality, fish presence and habitat a daunting task.
In addition, in order to conduct any sort of fish monitoring or habitat assessment, it is necessary to gain access permission from each of the numerous landowners who own the patchwork of private parcels along the stream banks.
As a result of these challenges, formal assessments of the stream system have been sparse, to say the least, and include one complete survey of Atascadero Creek by the California Department of Fish and Wildlife (CDFW) in 1969 and a partial survey of the upper reach in 1995. Jonive Creek was also surveyed by CDFW in 2001. Steelhead were observed in both streams but coho were not, despite the presence of relatively high-quality fish habitat in parts of the upper watershed.
California Sea Grant’s Russian River Salmon and Steelhead Monitoring Program (CSG) monitors the status and trends of native salmonids throughout the Russian River basin and conducts specialized research to support recovery efforts.
They have operated a trap on lower Green Valley Creek in most years since 2007 to temporarily capture and collect data on coho smolts (one year-old fish transitioning to the marine phase of their life cycle) migrating downstream towards the ocean each spring. On multiple occasions, wild coho smolts of unknown origin were found in the Green Valley Creek trap, introducing the possibility that those fish might have originated somewhere in the Atascadero system.
In search of juvenile coho, CSG biologists opportunistically snorkeled a few pools in Jonive Creek in 2015 and Redwood Creek in 2015, 2016, and 2017. They saw steelhead but not coho; however, those few pools represent only a small proportion of the fish habitat in each stream, so the lack of coho presence was not conclusive.
What makes Redwood Creek exceptional is the cold, clear water it contains—and contributes to Jonive Creek—even through the driest summer months. Ample perennial streamflow is a relatively rare and valuable asset in Russian River streams, many of which become intermittent or dry each summer. Indeed, insufficient summer flow is a significant bottleneck to recovery of local salmon and steelhead, who rely on freshwater habitat for juvenile rearing.
Last year, inspired by the perennial flow and instream habitat, the Russian River Coho Salmon Captive Broodstock Program—a collaboration that aims to re-establish a self-sustaining population of endangered coho salmon to the basin—decided to stock juvenile coho into Redwood Creek.
In December 2017, the US Army Corps personnel who raise the fish for the Broodstock Program released 3,041 coho young-of-the-year throughout 1,200 meters of the stream. Just over 600 of them (20%) were tagged with Passive Integrated Transponders (PIT tags) to allow for tracking at CSG fish monitoring stations, or antennas, in Green Valley Creek and throughout the larger Russian River basin.
The following spring, however, only two of the tagged fish released into Redwood Creek were detected passing over the antennas in lower Green Valley Creek on their way to the ocean.