Bioenergetics Studies

Fish occupying warmer water have higher metabolic demands than individuals in cooler water, and if these demands increase concurrently with a seasonal decline in prey availability, then growth rates may be reduced. [1]

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Updates

Links and Information Rainbow Trout Page Humpback Chub Page Aquatic Foodbase Page Nutrients Page Projects Natal Origins Project (NO) Presentations and Papers 2017 Boom-and-Bust Cycles in the Population of Rainbow Trout in Glen Canyon and Effect of Fall High Flow Experiments 2016 Yard et al. 2016. Seasonal and spatial patterns of growth of rainbow trout in the Colorado River in Grand Canyon, AZ. Canadian Journal of Fisheries and Aquatic Sciences Bioenergetic Modeling of Glen Canyon Rainbow Trout Fishery: Exploring effects of temperature, trout population size and biomass on benthic invertebrate consumption Prey size and availability limits maximum size of rainbow trout in a large tailwater--insights from a drift-foraging bioenergetics model 2015 Update on the 2015 decline in fish condition and abundance at Lees Ferry Rainbow Trout Growth, Condition, Population Dynamics and Modeling in Glen Canyon Drift-Foraging and Bioenergetics Growth Model for Rainbow Trout in the Lees Ferry Tailwater 2013 Fact Sheet: Native and Nonnative Fish Populations of the Colorado River are Food Limited--Evidence from New Food Web Analyses 2011 Petersen and Paukert. 2011. Development of a Bioenergetics Model for Humpback Chub and Evaluation of Water Temperature Changes in the Grand Canyon, Colorado River. Transactions of the American Fisheries Society, Volume 134, 2005 - Issue 4. Potential Policy Implications [2] Avoid boom-and-bust cycles to reduce trout export to LCR and maintain consistent catch rates and larger trout in the fishery: Enhance food supply via ‘bug flows’ or fertilization (add liquid nitrogen & phosphorous) as a mitigation for fluctuating flows and low reservoir elevation Limit recruitment via Trout Management Flows (TMFs) Do not implement fall HFEs in years when trout are in poor condition Fertilize prior to conducting an HFE to mitigate negative effects Critical uncertainties: Will TMFs be implemented & work? What years to implement (e.g., 2016)? Will bug flows or fertilization increase food supply? Does enhanced food supply increase or decrease extent of trout export? Monitoring Needs [3] STAY ON THE ROAD TO LEARNING: Estimate growth, survival, recruitment, and abundance by mark-recapture at time- scale that is fine enough to address GCD AMP questions. Response of recruitment to a particular flow in one year (e.g. spring HFE, 2011 equalization) Seasonal effects of fall HFEs on growth “Identify approaches to determine the root cause(s) of the unstable trout population in Lees Ferry” (#1 question) Measure export of trout from Glen Canyon to upper Marble Canyon (tagging not needed) The current Catch-Per-Effort survey provides imprecise indices of recruitment and abundance. Useful for assessing trends in population over longer blocks of time (e.g. 5 yrs), but not for tracking annual changes needed to address management questions. Growth is not estimated from CPE surveys but is needed to understand why recruitment and abundance are changing, and effects of fall HFEs. Two choices for TWG: Keep asking current management questions and therefore continue with mark-recapture program that can address these questions. Ask much simpler questions restricted to long-term trends in status which can be addressed from current CPE program. Other Stuff