Santa Ynez River Fisheries Studies

Steelhead are the ocean-going (anadromous) form of rainbow trout. They are born in freshwater, emigrate to the sea as juveniles to mature, and return to freshwater to spawn as adults. Steelhead in the Santa Ynez River historically migrated upstream to spawn and rear in the mainstem and tributaries throughout the watershed. Bradbury Dam, built in the 1950’s to create Lake Cachuma, is an impassable barrier to the migrating fish trying to access the prime habitat in the upper watershed. Therefore, the Fish Management Plan has focused on those creeks below the dam that offer the greatest opportunities to enhance aquatic conditions that will help supporting steelhead.

Fishery studies in the Lower Santa Ynez River downstream of Bradbury Dam have found that adult steelhead typically migrate upstream from the ocean from January through April, depending on rainfall. In years with limited rainfall, migration opportunities may be limited if insufficient runoff occurs to breach the sandbar at the lagoon. Adults captured since 1993 have ranged from 9 inches (resident rainbow trout) to 28 inches (adult steelhead). Spawning generally takes place between February through April, typically in the transition zone between pool and riffle habitats. Some spawning has been observed as late as May during high runoff years (1998). When steelhead/rainbow trout are ready to spawn, the female will excavate a depression in the substrate with her tail (termed a redd) where the eggs are eventually deposited and fertilized by one or more males. Once spawning is completed, the female will cover the fertilized eggs (redd) with gravel from the bottom of the creek. Females may build a several redds during the course of the spawning season. Once steelhead complete their spawning cycle, there are three things that can happen: 1) if flow conditions are good, the steelhead will follow the flow back downstream to the mainstem and migrates back to the ocean, 2) if flow conditions are low, the steelhead may decide to stay in the freshwater environment and oversummer until the next rain season, or 3) the steelhead will perish due to the physical demand during the spawning season. Only 30% of adult steelhead survive to spawn a second or third time.

Juvenile smolts (young steelhead) usually migrate out to the ocean to become adults between February through May. Juveniles spend 1-3 years in the freshwater environment before they migrate out to sea as smolts to become steelhead. Juveniles will spend 1-3 years in the ocean environment before returning to freshwater as adults. Due to the physiological changes necessary to respirate from freshwater to seawater, juvenile trout that begin the smoltification process will turn silver, losing most other color. Their scales become loose (deciduous) and their fin margins begin to darken.

Juveniles typically spend 1-3 years in the freshwater environment before they migrate out to sea to become steelhead. Outmigration occurs from February through March. Juveniles that decide to outmigrate are termed "smolts" and differ in appearance than trout that stay in the stream. Due to the physiological changes necessary to respirate from freshwater to seawater, juvenile trout that begin the smoltification process will turn silver, losing most other color. Their scales become loose (deciduous) and their fin margins begin to darken.