Simulating dam effects on river deformation and rainbow trout (Oncorhynchus mykiss) population number

In the downstream of the hydraulic power plant, the fish numbers are mostly affected by flow discharge, river deformation, temperature discharged from the reservoir. A dynamic population model have been developed and applied to the tailwater below Glen Canyon Dam, Arizona between 1991 and 2009 in order to estimate the effect of Glen Canyon Dam operation on rainbow trout habitat and population dynamics. Rainbow trout (Oncorhynchus mykiss) were selected as the target fish because they represent the major fish and monitored by Grand Canyon Monitoring and Research Center. Water depth, flow temperature, flow velocity and substrates types were used as the suitability parameters and corresponding suitability index curve were used to evaluate these indicators. Historic hydraulic data from 1991 to 2009 were analyzed to determine the minimum flow rate, mean flow rate and maximum flow rate, which were used to represent the Habitat Suitability Index (HSI) and Overall Suitability Index (OSI) in the study area of the rainbow trout life stage: fry, adult and spawning respectively. After that, a population model, integrating age structure population model and habitat model, were developed and used to calculate the fish abundance in the river and the simulation results also compared with observed fish numbers. Results indicated that under the historic dam operation the habitat suitability level in the Colorado River is not suitable for fry/larvae and spawning rainbow trout but very suitable for adult rainbow trout. It indicates that high HSI level does not mean high fish abundance.