DWR: Weber River, Evaluating habitat-based niche requirements for the bluehead sucker (Catostomus discobolus) population in the Weber River
March 2015 - June 2018
- Utah Division of Wildlife Resources
Many desert fishes in the USA are imperiled due to low perceived economic worth and over-allocation of water. Bluehead sucker (BHS; Catostomus discobolus), endemic to the Intermountain West, are protected by a multi-state conservation agreement, and the Weber River (Northern Utah) population, currently repressed and likely declining due a recruitment bottleneck, is one of the few outside of the Colorado River basin. Over-allocation of water, and the subsequent degradation of in-stream habitat, have resulted in a lack of slow-velocity habitat within the optimal thermal range for BHS. Our objectives are to determine whether degraded habitat conditions limit the BHS population in the Weber River. We are locating preferred habitat of spawning and rearing BHS and quantifying habitat characteristics and availability using reach-based surveys. After locating spawning areas primarily in the lower-elevation reach of the Weber River (i.e. near Ogden), we divided the river into 300-m reaches and surveyed all spawning reaches and ten randomly-selected non-spawning reaches for substrate, depth, cover, and habitat units (i.e. riffles, pools, backwaters). Preliminary results suggest that gravels (11-32 mm in diameter) and pools (average size: 194 m², > 1.5 m max. depth) are important components of spawning habitat in the Weber River, while backwaters that are larger (range: 3-109 m³) and deeper (range: 25-87 cm) provide rearing habitat for the most sucker larvae and juveniles. Future efforts will include comparing our results to BHS preferred habitat in a river system with a healthy BHS population, likely the Raft River in northwestern Utah, and laboratory experiments to determine ideal microhabitat (velocity and temperature) for juvenile BHS. By evaluating the habitat needs of the native and imperiled bluehead sucker, this study will help inform future conservation and restoration efforts directed at this declining population.