Difference between revisions of "Bioenergetics Studies"

• Rainbow Trout Page
• Humpback Chub Page
• Aquatic Foodbase Page
• Nutrients Page

• Natal Origins Project (NO)

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.

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?

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.