Changes to One California Creek Could Benefit the State’s Trout

Go fishing west of the Mississippi and you’re liable to catch a rainbow trout, one of the most ubiquitous species of fish in the western United States. But just because a species of fish is found in numerous bodies of water across the nation doesn’t necessarily mean that all of its habitats are uniformly hospitable. And when it comes to the Arroyo Seco, which feeds into the Los Angeles River, a recent study concluded that some substantial changes may be needed in order for the trout living there to thrive.

The report was prepared by the environmental consulting firm Stillwater Services, and focuses on the Stream Flow Enhancement Program for the Arroyo Seco. At issue here are the barriers within the Arroyo Seco that prevent the trout within from traveling to the ocean and back, part of the anadromous behavior characteristic of some of the species. A quick aquatic primer: rainbow trout and steelhead trout are the same species, O. mykiss. Steelhead trout are those who begin their lives in fresh water, migrate to salt water and eventually return to fresh water in order to spawn.

Stillwater Services’ analysis suggests that the trout in the Arroyo Seco are descended from steelhead trout; unfortunately for them, structures built on the tributary (including Devil’s Gate Dam) have blocked them from returning to the ocean.

The consultants go on to point to the existence of “9 anthropogenic barriers within the upper Arroyo Seco [which] impede the natural movement patterns of O. mykiss.” They note that removing these will not be easy, and will require the involvement of numerous stakeholders.

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That said, similar programs have been implemented elsewhere in the country that have benefitted the aquatic populations. “[T]he idea is to remove some of these barriers so the fish can move up and down the stream as necessary to survive,” the head of the Arroyo Seco Foundation, Robert Kurkjian, told the Los Angeles Times. As the Times pointed out in its coverage of the study, rainbow trout are not endangered, but steelhead trout are, and this initiative could help bolster that population.