Razorback Sucker Spawning in an Intermittent Colorado Tributary

Abstract

AbstractEndangered and endemic Razorback Suckers Xyrauchen texanus of the Colorado River basin largely spawn in main‐stem rivers and reservoirs. While documenting other native fish use of two intermittent tributaries of the Gunnison River, Colorado, USA, we detected PIT‐tagged Razorback Suckers during the 2015–2019 spawning seasons (April–June) and captured reproductively ready individuals. Because the species is rarely documented in small tributaries, we highlight this occurrence. Prior to 2019, up to 30 individual Razorback Suckers were detected annually in Roubideau Creek, a tributary to the Gunnison River near Delta, Colorado. In 2019, use increased as we detected 110 individual Razorback Suckers in Roubideau Creek, and, for the first time, we handled or detected seven in Cottonwood Creek. These fish represented multiple age‐classes of hatchery‐reared fish repatriated to the Gunnison River to aid recovery. We collected and identified 1,171 larval catostomids from Cottonwood Creek, but none were Razorback Suckers, and even though ripe adults were collected, it remains unclear if reproduction occurred. We suspect that high runoff in 2019 drove increased use of the system. Presence of Razorback Suckers in five consecutive years indicated that intermittent tributaries might be of greater importance than previously thought for this species, and these streams warrant further investigation and protection.