7908 - Laserfiche WebLink

Home Browse Search

Final Report 1993 large numbers of young began to descend to the mainstem in July, during low and clear flow in the LCR The 1993 cohort was large and movement to the mainstem during low flows in July 1993 suggested that dispersal was density-dependent, and the result of food shortage or habitat limitation in the LCR RECOMMENDATIONS 1. Integrate LCR and Mainstem Data: Much valuable information on the aquatic ecosystem in Grand Canyon has been collected in the past 10 years, but the value of this information is not entirely apparent because it presently lacks integration Analyses and interpretation of data collected in past and ongoing investigations of fishes, macroinvertebrates, primary and secondary production, water quality, and geomorphology need to be conducted, and possible linkages identified to test hypotheses presented in the Draft Integrated Research Plan. This information also needs to be integrated and further analyzed to better define future core research and long-term monitoring strategies. An assimilation of information will help researchers develop better scopes of work that can use existing information, minimize repetitive data collection, and develop more directed hypotheses that address cause and effects of operations. The framework for a Grand Canyon Fisheries Integrated (GCFIN) database,(Brown et al. 1995) has been developed (Supplement No. IV), 2. Develop a Population Model: A population model is CWTently being developed by Ryel and Valdez (1995) (Supplement No. V) as a means of determining the status and trend of the humpback chub population in Grand Canyon, by integrating empirical data collected by the GCES investigations. 3, Integrate Geomorphology with Fish Habitat: The relationships of channel geomorphology and fish habitat identified by this investigation need to be described and used to help evaluate the likelihood of a second spawning population ofhwnpback chub, as well as the effects of high spring releases, and steady summer flows, Executive Summary . 19 4. Develop a Non-Native Fish Management Plan: Predation may be a major source of mortality for subaduIt humpback chub in Grand Canyon. Major predators need to be identified, their impact quantified, and control options discussed. Sensitive areas need to be identified, such as the blue ribbon tailwater trout fishery and the rainbow trout at Nankoweap Canyon used by migrating bald eagles. 5. Develop a Genetics Management Plan: The last recognizable mainstem stock of humpback chub in Grand Canyon may be represented by 40-60 adults near RM 30, some of which are spawning in the warm springs of Fence Fault. Management strategies need to be identified for taking fish to a refugia or enhancing mainstem spawning and survival. 6. Evaluate EIS Elements: Risk assessments are recommended for evaluating selective withdrawal, high spring releases, and steady summer flows. 7. Conduct Swimming: Perfonnance Experiments: Hypotheses need to be tested that sub adult humpback chub are being transported downstream and limited to low velocity habitat by reduced swimming performance at cold temperatures. We recommend laboratory swimming performance tests for yay (range, 50-100 rom TL) and juveniles (range, 100-200 rom TL) at 1OoC, 1rC, 150C, and 200C following acclimation to 200C; these conditions simulate young fish moving from the LCR to the mainstem. 8. Develop Depth and Velocity Isopleths of River Channel: Additional mapping of the river bottom and velocity characteristics is recommended with SuperHydro technology. 9, Determine Relationship of Drift and Benthos: Concurrent sampling of drift and benthos is recommended to characterize macroinvertebrate communities by season, time of day, flow magnitude, and ramping rates. 10, Identify Sources of Primary and Secondary Production: The hypothesis should be tested that food supplies for sub adults are limiting in western Grand Canyon in order to determine if