Coastal Rainbow Trout (Oncorhynchus mykiss irideus)

January 2022

Female rainbow trout in hand California’s trout is a cornerstone of California freshwater angling and we are lucky enough to have a highly productive wild trout fishery right in our backyard in the Interdam Reach! The Interdam Reach is an 8-mile stretch of Putah Creek between the Monticello Dam of Lake Berryessa and the Putah Diversion Dam just beyond Lake Solano. The major species of trout you will find in the Interdam Reach is the native winter-spawning Coastal Rainbow TroutOncorhynchus mykiss irideus. Unlike the anadromous Central Valley Steelhead, Oncorhynchus mykiss, the California Coastal Rainbow Trout spends its entire life in freshwater.

Coastal Rainbow Trout are the most widely distributed trout in California, from the coast of the Pacific Ocean to the western slopes of Sierra Nevada. Self-sustaining populations of coastal rainbow trout are defined as being physically isolated by natural (waterfalls, landslides) and anthropogenic (dams) barriers or being introduced by humans to isolated areas (high elevation lakes). They exhibit an extremely diverse range of coloration and patterning, but most coastal rainbow trout have heavy spotting concentrated on their dorsal side and a thick reddish pink “rainbow” band down their sides. As a result of human introduction, whether it be pack mule train or airplane, coastal rainbow trout are now more abundant in California than ever before. In fact, rainbow trout are included in the top 100 list of globally invasive species. Despite their wide distribution and extreme abundance, coastal rainbow trout have likely suffered a decline due to more frequent and more severe droughts.

Rainbow troutIn 2014, the California Department of Fish and Wildlife designated the Interdam Reach of Putah Creek as a Wild Trout Water. A Wild Trout Water designation means that the Interdam Reach supports a self-sustaining trout population, provides adequate fish catch rates, and is open to public angling. The Heritage and Wild Trout Program of CDFW aims to protect, enhance, and restore California’s heritage and wild trout resources. To do this, resource management plans have been implemented to improve in-stream and riparian habitat and water quality.

After the cessation of supplemental stocking in 2008, the Interdam Reach has a year round zero harvest policy. In other words, fishing is catch and release only. The Interdam Reach is also limited to artificial flies and lures with barbless hooks. While state regulation states that open season is year round, there is an unwritten rule that the creek should not be fished during Putah Creek’s trout spawning season. While most of California’s trout spawn during the spring to early summer, Putah Creek’s coastal rainbow trout spawning and the voluntary closure lasts from December 1st to March 1st. The cessation of fishing during spawning season is so important because there are reduced winter flows from the Monticello Dam and there is also limited spawning habitat, also known as redds, within the Interdam Reach.