T. Hicks and T. Bonaquista conduct electrofishing surveys of endangered fish on the Colorado River near Moab, Utah, 2004. Captures of tagged and untagged Colorado pikeminnow allow researchers to annually estimate population abundance in the Colorado River. Photo by D. Osmundson.
The Colorado River Fishery Project conducts research on the life history of the four endangered Colorado River fish and the habitat that supports them. Knowledge of the biology of the fish and their ecological requirements is essential to understanding the threats the fish face and to developing management strategies for their recovery. Studies have included such subjects as timing and location of spawning, distribution and relative abundance of larvae and young-of-the-year, dispersal patterns of adults, seasonal habitat requirements, growth rate, survival rate, sex ratio and food habits. Habitat studies have focused on the effects of various flow regimes on habitat suitability. Availability of preferred mesohabitats (pools, eddies, backwaters, etc.) vary depending on flow stage. Additionally, such habitats are generally formed during large spring-flow events. The quality of the substrata (river bottom sediments) that produce algae and benthic invertebrates, the base of the food chain, are affected by flows. Seasonal water temperatures that affect feeding rates and timing of spawning are also affected by flows and river regulation. Hence, assessing the suitability of the environment for the endangered fishes requires linking our knowledge of their biological requirements with our understanding of how flows affect the quality of their physical habitat. Equally important is understanding how the endangered fish interact with other members of the biological community, i.e., the foods they feed on and the predators that feed on them. Hence, research is a critical prerequisite to devising effective management actions.
J. Carrillo removes fish from a trammel net set at the mouth of a Colorado River backwater in Canyonlands National Park, 2005. Photo by D. Osmundson.
Aquatic invertebrate samping helps researchers assess effects of flow and fine sediment accumulation in the river-bed. Photo by D. Osmundson.