Voices of Walker Creek Watershed: David Hines
by Alisan Theodossiou, CalTrout Senior Communications Manager
David Hines is a Senior Environmental Scientist and the Coho Salmon Recovery Coordinator with the California Department of Fish and Wildlife.
Historically, Central California Coast (CCC) coho salmon were abundant, yet today there are few salmon remaining. Walker Creek is one of the many watersheds that have lost their coho salmon population. However, over the last 20 years have returned, largely due to recolonization and restoration efforts by organizations such as the California Department of Fish and Wildlife (CDFW), one of California Trout’s key conservation partners. With aspirations to continue improving watershed conditions, resource agencies and organizations have been coming together to support the return of coho salmon to Walker Creek once again.
Coho salmon pair. By Eric Ettlinger.
David Hines, CDFW’s Coho Salmon Recovery Coordinator, has made it his goal to apply the best available science to better understand these fish and to support the conservation and restoration efforts in the watershed. “We’re asking ourselves: ‘Are the adults returning to the watershed? Are they able to access spawning areas? Are they successfully spawning? Are juveniles getting enough cold water in the summer for them to survive?’ I really enjoy the science side of my work, the unraveling of these important questions,” explains David.
Opportunity for Salmon Recovery
As to why coho salmon are important in Walker Creek, “CDFW and partners have been focused on the Walker Creek population because it has strategic value for recovery. Larger watersheds, like the Russian River and Lagunitas Creek, intrinsically have the potential to provide enough habitat to support viable populations. For smaller watersheds like Redwood Creek, the lack of space leaves it unable to support a viable population in the long run. Walker Creek is a medium-sized watershed but is large enough to have strong potential as an independent population. Another advantage to this population is that nearby Lagunitas Creek is performing very well in supporting coho salmon. It’s helpful to have populations close together so that they can salvage each other if one population is struggling.”
While Lagunitas Creek currently supports only a small fraction of its historic run size, it stands out as one of the largest existing populations in the CCC coho salmon Evolutionary Significant Unit (ESU). For this reason, Lagunitas Creek coho salmon contribute important genetic diversity to neighboring populations. It is also an important source of fish for the Coho Salmon Captive Broodstock Program (CBP), which has played an important role in preventing the species’ extirpation (i.e. extinction) in the Russian River watershed. The program also supports the release of adult and juvenile coho salmon into Walker Creek as a critical component of salmon recovery efforts. Conservation hatcheries such as this are much different than traditional production hatcheries and are used to raise threatened and endangered fish that are nearing extinction in the wild. Intentional pairing of adults based on genetic relatedness helps keep offspring as similar as possible to wild fish so that they have the best chance of survival in ecosystem upon which they depend. Click here to read more about conservation hatcheries.)
Applying Science and Conservation
For Walker Creek, adult coho salmon releases have been going on since 2004 using fish from the CBP. David explains, “these releases are a big reason why we conduct fish monitoring in Walker Creek. Initially, there was no monitoring to determine whether the re-stocking was working, whether the fish were distributing themselves in the watershed, whether they were pairing up and spawning and successfully creating offspring, and whether those offspring survived and made it out to the ocean.”
Coho salmon’s habitat needs are very specific; they require a rich, complex stream system with dense canopy cover, ample fallen and live wood in the stream, clean spawning gravels, cool deep pools, and oxygen-rich water. They also rely on a steady supply of food which is mostly comprised of aquatic insects that thrive in watersheds with good water quality.
“We still have questions about habitat quality Walker Creek watershed and whether it’s sufficient to support these fish. We have started ramping up our monitoring there to answer those questions and CalTrout has been a terrific partner with us in these monitoring efforts,” said David.
Monitoring salmon and their habitats in Walker Creek is critical to informing restoration and conservation efforts in the watershed. “One thing that’s fascinating about salmonids is that they cross many habitat boundaries as they transition between life stages. Basically, they rely on different habitat features at different life stages. With their survival dependent on so many habitat elements, there is a lot of room for things to go wrong. If we find that survival at a certain life stage is declining, it’s imperative that we understand what’s happening there. Understanding what is limiting the population is challenging, but it is an essential prerequisite to applying efficient and effective restoration actions. For example, concern over low juvenile abundance has led us to investigate spawning gravel quality in Walker Creek. If the results of this study show high levels of fine sediment in spawning gravels, restoration actions can be designed to reduce gullying and other forms of erosion in headwater streams,” said David.
Collaboration with the Community
The Walker Creek watershed still supports many dairy farms and other ranching and agricultural operations. Historical practices contributed to extensive changes in ecosystem structure and function via erosion, sedimentation, and loss of riparian habitat. Habitat degradation has been a major factor in the decline of coho salmon populations.
Today, however, many landowners in the watershed are supportive of restoration and bringing back the salmon. Over 50% of ranches in the Walker Creek watershed have participated in conservation projects during the last 30 years. David remarks, “I see landowners in Walker Creek watershed collaborating and working with organizations to help reduce impacts, such as fencing off streams to protect them from grazing. Those landowner partners that we’ve been working with have been tremendous. Walker Creek Ranch, for example, and the Brazil family have been amazing. They are friendly, cooperative, and have been very generous in allowing us to get access to the creek to (for example) set our downstream migrant trap and PIT antennas1. There are still other landowners that we are working establish relationships with since we still don’t have access to a lot of the watershed and are hoping to expand our monitoring and restoration work.”
Hopeful Results
When collecting fish, CDFW also retains small tissue samples for genetic testing. Scientists can then analyze those samples to determine whether the parents were of hatchery origin or not (presumed wild). This is one way to measure the extent to which the population can survive on its own. The downstream migrant trap was installed in lower Walker Creek thanks to the help of participating ranches that gave access to the site. David explained, “Our main goal in trapping is to measure how many coho smolts are migrating out to the ocean. Last year, we captured just over 2,000 smolts; I had expected that the vast majority of those would be hatchery-origin fish.”
However, David’s expectations were fortunately incorrect. “When we release hatchery-raised fish into the creek, they are all tagged, so we know when it’s a hatchery-origin fish or not. In 2022, we discovered that the majority of smolts captured were of natural origin. This is a good indication that wild fish are successfully reproducing on their own. It’s encouraging to see some natural production happening; it points to the success of our population recovery efforts.”
1 Downstream migrant traps collect juvenile salmonids as they migrate to the ocean as smolts. It’s an important measure of population performance. Passive Integrated Transponder (PIT) antennas detect hatchery juvenile and adult coho salmon that have been implanted with PITs (the same technology as chips placed in cats and dogs) as they migrate to and from the ocean.
