What is the difference between Rainbow Trout and Steelhead? There is none, at least on a genetic level. They are the same fish, but we call them Steelhead if they go out to the ocean for a timebefore coming back to spawn, and we call them Rainbow Trout if they stay in the creek they’re born in to grow up and spawn. How can we tell them apart? Steelhead come back from their adventures bigger and with different coloring than their Rainbow counterparts. There is more food out there, but also more predators.
To go, or not to go? This is an important life choice for these fish, and one that is generally made for them in urban areas. The creation of roads forces creeks into underground culverts, while dams create a full stop in the creek. So many barriers to fish passage exist in urbanized areas that it’s hard for fish to make it out to the ocean, let alone find their way back. Luckily, community groups around the Bay Area are working to reconnect local creeks to the bay. The Alameda Creek Alliance has worked for 20 years to remove barriers to fish passagein Alameda Creek, removing five dams and constructing three fish ladders in the process. Currently, the San Francisco Public Utilities Commission is re-structuring the Alameda Creek Diversion Dam to allow fish to move between the upper and lower watershed, a project that is set to complete in 2018.
A million-dollar project was just completed on Pinole Creek to allow fish passage under the I-80 freeway, thanks to years of planning by the Friends of Pinole Creek and the Contra Costa Resource Conservation District. When the freeway was built in the 1950s the creek was culverted into two box channels underneath, preventing almost all steelhead from making it upstream. This retrofit project involved creating a backflow of water in the downstream portion of the culvert,and providing a ladder-like sectioncut into the upstream portion to help fish climb (see video here).
And we’ll be glad to have them back! Rainbow Trout and Steelhead play an important role in creek ecosystems, which can be quite complicated. Primary producers such as algae use light and nutrients to produce oxygen; the algae is eaten by benthic macroinvertebrates (bugs that live at the bottom of the creek) who also eat detritus and each other. Trout eat the bugs, as well as other smaller fish and fish eggs. (A lot of intra-level feeding goes on.) Anything that dies in the creek moves to the bottom, where it decays and is consumed by bacteria, who use oxygen and produce carbon dioxide. Rainbow Trout and Steelhead are an important indicator species in creeks, because they need cold, oxygen-rich flowing water to live and reproduce. If you see them in your creek, that’s a good sign!