Expansion of Shimofuri Goby (Tridentiger bifasciatus) from the California State Water Project to the Santa Clara River, Ventura County, California

Shimofuri gobies (Tridentiger bifasciatus) were first discovered in San Francisco Bay in 1985. This species eventually dispersed through the California State Water Project (SWP) aqueducts to various reservoirs in southern California and was first reported in 1990 in the SWP’s Pyramid Reservoir located on Piru Creek, a tributary to the Santa Clara River in Ventura County. Shimofuri gobies were subsequently reported in Piru Creek below Pyramid Dam. Shimofuri gobies were later observed in 2013 below Lake Piru’s Santa Felicia Dam. Following a short storm in March 2014, nine Shimofuri gobies were collected in a fish trap at the Freeman Diversion on the Santa Clara River located approximately 27 miles downstream of Lake Piru and 10 miles upstream from the estuary—the first report of this species in the mainstem Santa Clara River. These data indicate that Shimofuri gobies are likely to be present in the Santa Clara River estuary, which is home to the federally endangered tidewater goby (Eucyclogobius newberryi). Shimofuri gobies are likely present in most reservoirs within the SWP in southern California. There are no known implemented management strategies to monitor or prevent future invasions through the SWP to drainages receiving state water.