Gone are the days when coastal streams in San Luis Obispo County teemed with large steelhead trout. Migration barriers and habitat destruction over the past century have reduced the numbers of the iridescent fish to a fraction of their historic levels.
However, the fish are beginning to stage a comeback, thanks to the coordinated restoration efforts of numerous conservation groups and government agencies. That’s the conclusion of the state Ocean Protection Council in a recently published resource evaluation.
According to the report, 18 streams in San Luis Obispo County have historically had steelhead. Of those, five are considered regionally significant including Arroyo de la Cruz, Santa Rosa, Chorro, San Luis Obispo and Arroyo Grande creeks.
Steelhead are an anadromous form of rainbow trout. Like salmon, they spend most of their lives in the ocean but spawn in freshwater rivers and streams.
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Fish south of the Golden Gate must spawn in streams that experience significant seasonal fluctuations in flow, creating an additional challenge for them. Steelhead in San Luis Obispo County are listed as “threatened” under the federal Endangered Species Act.
The largest steelhead watershed in the county is San Luis Creek, which covers 85 square miles and accounts for about a quarter of the available rearing habitat. Including tributaries, it holds 30 miles of stream habitat.
A 2008 assessment put San Luis Creek’s steelhead population at 37,000 fish, most found in the lower reaches of the creek. They range from Avila Beach to the foot of the Cuesta Grade at Stagecoach Road.
“There’s a healthy number of fish in the creek,” said Freddy Otte, San Luis Obispo city biologist. “The watershed is basically open, and the habitat as a whole is pretty good.”
That’s due to the efforts in recent years of various agencies as well as the Land Conservancy of San Luis Obispo County to improve San Luis Creek as steelhead habitat. Similar efforts are under way in other creeks, such as Chorro Creek, the main creek flowing into Morro Bay.
Steelhead face several modern challenges when they swim upstream to spawn, said Jon Hall, watershed restoration coordinator with the Morro Bay National Estuary Program. Restoration efforts focus on removing these problems. They are:
Barriers: These are man-made structures, such as dams, weirs and culverts, which prevent steelhead from swimming upstream.
Sedimentation: Steelhead need clean gravel beds, called redds, to spawn in. Erosion releases sediment into creeks that covers redds with silt. Bank stabilization is a way to minimize silting.
Low flows: Steelhead need a healthy flow of water to swim upstream. Reducing irrigated agriculture from areas adjacent to the stream leaves more water for in-stream uses. A Fish and Game wildlife refuge below Hollister Peak, which used to be an avocado orchard, serves this function for Chorro Creek.
Invasive species: Many non-native plant species clog streams and suck up large amounts of water. Steelhead in Chorro Creek also face competition from non-native pikeminnows.
With many of these barriers removed, steelhead are now being found in some unlikely places. Dennis Michniuk, district fisheries biologist with the Department of Fish and Game, said he once found several dead adult steelhead in an unnamed tributary off Tank Farm Road in San Luis Obispo that had probably died after spawning.
“They are pretty tough fish,” he said. “I even see a lot of fish in the creek tunnel downtown.”Healthy steelhead populations like this serve an important function. They can establish new populations in other coastal streams in the area, Otte said.
In addition to the Land Conservancy and Estuary Program, Central Coast Salmon Enhancement, California Conservation Corps and Coastal San Luis Resource Conservation District have been active in steelhead restoration work. They have banded together to form the Central Coast Steelhead Initiative to coordinate activities, Hall said.
These groups work with their counterparts in Santa Barbara and Ventura counties as part of a group calling itself the Tri County Fish Team. They are guardedly optimistic about the long-term outlook for steelhead.
More work on many levels still needs to be done to ensure the survival of the species, Otte said.“A healthy ocean environment is also needed to get a full recovery, so it is not clear whether the fishery can ever recover to its historic levels,” he said.
For more information about the Southern Steelhead Resources Evaluation, go to www.opc.ca.gov.