depths go from a few centimeters to over 1 m (3 ft 3 in). The rivers they swim in are at a cool temperature (average of <22 °C), with variable flow as they are well-adapted to survive in the most-intense flood conditions. Not surprisingly, given their feeding method, they prefer gravel, rubble, and boulder substrates. In 2010, USF&WS issued an expanded CH determination for the Santa Ana Sucker. 75 Federal Register 77962 (December 14, 2010). Range The Catostomus santaanae range is extremely restricted; they are native only to the Los Angeles, San Gabriel, Santa Ana, and Santa Clara River systems in Southern California. Populations have been lost from several parts of the rivers, so that they now only live in Big Tujunga Creek in the Los Angeles River Basin, the headwaters of the San Gabriel River in the San Gabriel Mountains in Angeles National Forest in Los Angeles County, parts of the Santa Clara River system in Los Angeles and Ventura counties, and the lower part of the Santa Ana River in Orange County, especially areas with additional water effluent from sewage treatment plants. A substantial fish population can also be found in a research-monitored project in Los Angeles County of Haines Creek. Conservation Since Santa Ana Suckers have been enlisted as an endangered species (April 2000), the Santa Ana Watershed Project Authority has been actively working towards conservation efforts through direct administrative action and educational opportunities for the public to become aware of. Watershed conservation efforts are key in saving these suckers as their biggest threat posed is of habitat lose where it is recorded that they currently have lost over 95% of their natural habitat. Although some stretches of the rivers are 'wild' and protected by being within the Angeles National Forest area of the San Gabriel Mountains, the coincidence of this fish's range and the Greater Los Angeles metropolitan area, and flowing in concrete lined flood control channels, means that it is a species vulnerable to extinction. The International Union for Conservation of Nature has rated this fish as an "endangered species" because of its decreasing area of occupancy and declining population. References Peter B. Moyle, Inland Fishes of California (University of California Press, 2002), pp. 182–185 santaanae Endemic fauna of California Fish of the Western United States Santa Ana River ESA threatened species Fish described in 1908