Steelhead Demographics from Two San Luis Obispo County Creeks

Oncorhynchus mykiss (O. mykiss), commonly known as steelhead or coastal rainbow trout, is native to San Luis Obispo County, California.  Steelhead in San Luis Obispo County are currently listed as a threatened species.  The effects of a growing and expanding human population are currently detrimental to the survival of O. mykiss.  Residential, agricultural, and industrial land development has impacted the habitat utilized by steelhead resulting in sedimentation, pollution, and reduced water flow.  Research must be conducted to better understand the status of threatened steelhead populations in order to implement more relevant management and restoration plans. 

Currently, little is known about the demographics of the steelhead trout in San Luis Obispo County.  Specifically, demographic information including length, age, and condition when first leaving a watershed for the open ocean is lacking.  This project will take a closer look at the steelhead populations from two north county coastal streams, San Simeon and Santa Rosa Creeks. 

Outmigrant trapping was conducted on each creek to survey the population of trout as they migrate downstream to the lagoon or ocean.  Demographic information was collected from each fish, analyzed, and compared between the two populations of O. mykiss.  Additionally, electrofishing surveys were performed within each watershed and subsequent steelhead data was compared between two different years.

Information was collected regarding the steelhead habitat of San Simeon and Santa Rosa Creeks.  Stream habitat mapping was performed to evaluate the condition of the environment where the steelhead reside.  Annotation of applicable spawning and rearing habitat was recorded and comparisons were made between the habitat of these two creeks.

Data generated from this study will benefit these steelhead populations by identifying differences and similarities which may contribute to their preservation and management.  General information on the steelhead demographics from San Simeon and Santa Rosa Creeks will increase the knowledge about threatened steelhead populations on the central coast of California.  Further more, information on steelhead habitat attributes, when analyzed along with current population demographics, may assist governing bodies when making decisions that involve these watersheds and their threatened O. mykiss populations.