By Elliott Thompson
Humans are not the only ones impacted by drought. One species that is also vulnerable is the steelhead trout. One hundred years ago, steelhead trout were commonly seen in ocean and bay waters as well as streams ranging from Santa Cruz to Sonoma County. Oncorhynchus mykiss found the region’s mix of salty and fresh water an ideal habitat, preferring coastal waters and tributary streams. Unfortunately, their numbers plunged in the 20th century due to habitat degradation.
Steelhead and rainbow trout are often called the same thing, and that’s because they are, at least genetically speaking. Steelhead actually are rainbow trout that migrated out of fresh water as juveniles and spent a portion of their lives in the Pacific Ocean before making the journey back to fresh water to spawn, thanks to their homing behavior. According to the California Department of Fish and Wildlife, adult California Steelhead are usually at least 16 inches in length. Wild steelhead may not be caught and must be immediately released if any accidental captures occur.
The life-cycle of steelhead can be seen as five distinct stages: the egg, fry, smolt, adult and spawning stages. Spawning requires eggs deposited in gravel where the velocity of the water is high enough to oxygenate it. Fry will hatch in late spring or early summer and live in streams for one to two years. Smolts migrate downstream and enter the ocean in early spring.
Some creeks along San Francisco Bay have been determined to be “anchor habitat” for the species, whose population in bayside streams has been decimated. Pollution, habitat destruction and now the extended drought have all contributed to the already plummeting survival rate for steelhead to drop even more. Streams and creeks are drying up, devastating to the population of trout.
But there is hope: restoration work in a number of locations around San Francisco Bay will begin soon. For example, in Pinole, the city and a number of public agencies have joined together to construct a fish passage under I-80. The juvenile fish in the upper watershed will finally have a way out to the bay, and adult steelhead will no longer be blocked on their journey up the creek to spawn. This beautiful creek has much of its reach in the upper watershed on EBMUD land where there is little human influence, providing excellent habitat for the fish. There are plenty of overhanging branches, rooted areas, and undercut banks where juveniles can eat a variety of aquatic invertebrates such as mayflies, caddisflies and stoneflies.
Steelhead are a good indicator of the overall health of aquatic and oceanic systems and therefore need to be monitored carefully. The steelhead could very well be the canary in the coalmine.
