Restoring salmon or trout spawning grounds requires knowing the characteristics that make a suitable environment for fish reproduction. FISHBIO performs annual surveys of redds, the gravel beds where salmonids lay their eggs, in several Central Valley streams to evaluate Chinook salmon and steelhead/rainbow trout spawning preferences. We document the temporal and geographic distribution of redds using boat and foot surveys, and measure stream conditions such as river flow velocity, water temperature, depth, and substrate type. The results of these surveys can help guide restoration efforts and inform water managers of the river flows and water temperatures needed to maximize spawning habitat area. If the river flow drops during spawning season, fish may strand out of the water before they can reproduce.