Stream

Each fall, the Juvenile Steelhead & Stream Habitat (JSSH) monitoring program measures population density and assesses habitat quality for steelhead across four watersheds in Santa Cruz county. Within each watershed, different sections of stream, known as reaches, are defined based on similar characteristics such as: gradient, channel width, substrate, and habitat types. Fish and habitat sampling is conducted along half-mile stream segments within each reach. Each half-mile stream segment is habitat typed to assess stream conditions. Habitat typing involves identifying specific habitat units (riffles, runs, pools), measuring stream depth and width, and assessing substrate and cover. Fish sampling sites are chosen based on average habitat quality within a segment, with a focus on pool length, depth, and cover. A typical sampling site consists of two pools and any adjacent runs and riffles. Sampling sites differ in total length due to the unique composition of pool, riffle, and run habitats. To compare steelhead counts across sites, the JSSH program reports steelhead density: the total number of steelhead per 100 feet of stream. The steelhead densities include both the counted (captured) steelhead and an estimate of any steelhead that may have evaded capture. The number of escaped fish are estimated with a formula based on the rate of capture from the electrofishing process. For the best chance to survive to adulthood, steelhead need to be at least 150mm when they migrate to the ocean in spring.The JSSH program measures steelhead in autumn and assumes that fish longer than 75mm will be big enough by spring to migrate to the ocean. Fish that are smaller than 75mm in autumn will likely need an additional year in freshwater to grow before migration. Due to these important size constraints, JSSH reports steelhead density for two size classes: steelhead that are shorter than 75mm and steelhead 75mm or longer.