Status and distribution of Arroyo Chub within its native range

Abstract

The Arroyo Chub (Gila orcutti) is a small cyprinid native to coastal drainages of Los Angeles, Orange, Riverside, and San Diego counties. We surveyed the seven drainages historically known to support the species in 2012-2014 and again in 2019 to determine current range and distribution. We compared our results to the most recent species account we could locate (1993). We detected Arroyo Chub in 18 of the 40 streams (45%) and within six of the seven native watersheds in our 2012-2014 surveys, while our 2019 surveys located fish in all of the seven native watersheds. This native species has retreated to the headwaters in most watersheds and the number of populations have declined since the most recent species account. Non-native species, habitat loss, urbanization, water development, flood control, and drought are thought to be the primary causes of this decline.