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Project O.1.c - A review of methods to determine prey consumption rates, gastric evacuation and daily ration of pelagic fishes: a precursor to experimental estimation for key predators in the EPO

01 Jan 2019 - 31 Dec 2021

Program(s) in charge: Ecosystem & Bycatch Program
  • Review available methods to estimate prey consumption and gastric evacuation rates and daily ration to reliably estimate the consumption biomass ratio (Q/B) for tropical tunas and tuna-like fishes in ecosystem models being developed for the EPO.
  • Recommend a reliable method(s) that is feasible, practical and cost-effective for estimating Q/B for key predators in the EPO ecosystem.
  • Fisheries management strategies are increasingly considering impacts on ecosystems supporting target tuna species. Tuna fisheries impact apex predators in marine ecosystems and have the potential to disrupt ecosystem structure and function.
  • Ecosystem models, such as Ecopath with Ecosim, are being increasingly used to explore and forecast the potential effects of fishing and climate on marine ecosystems.
  • A key parameter in such models is Q/B. However, this highly influential parameter can be difficult to estimate experimentally, especially for large pelagic fishes.
  • A review of methods to estimate Q/B is required to determine which methods are feasible for parameterizing ecosystem models.
Relevance for management
The Antigua Convention requires the IATTC to consider the ecological impacts of tuna fisheries in the EPO. The staff has detailed plans to develop a spatiallyexplicit ecosystem model of the EPO in moving towards an ecosystem approach to fisheries management. Without reliable estimates of Q/B for key species in the EPO ecosystem, the ecosystem model will produce unreliable results that will be of little use for tactical or strategic fisheries management.
3 years
Workplan and status
  • Jan–Mar 2019: Collate all available literature on methodologies used to estimate prey consumption and Q/B in marine fishes, with an emphasis on predatory pelagic fishes.
  • Mar–Apr 2019: Write a comprehensive literature review of methods to estimate Q/B and make recommendations as to which method(s) may be useful for IATTC to use in the future.
  • May 2019: Present the review document at SAC-10 and at the 70th Tuna Conference
  • Jun–Dec 2019: Revise the review document for submission to a peer-reviewed scientific journal.
  • Jan-June 2020: Simulations and sensitivity analyses of a bioenergetics model for inclusion in the review document.
  • July-Dec 2020: Proposal considerations for consumption and gastric evacuation experiments of dolphinfish. Refinement of input parameters for several predatory species and development of a new age-structured consumption model.
  • Jan-May 2021: Continued development of the consumption model; simulations and uncertainty analyses.
External collaborators
University of Miami for proposed laboratory experiments
  • Information paper for SAC-10
  • Publish the literature review in an international scientific journal.
Updated date: 01 May 2022
Progress summary for the reporting period
  • Review manuscript revised to update method descriptions in text and tables. 
  • Yellowfin tuna feeding, growth, metabolic, and reproductive data were compiled as input data for bioenergetics models using Fisheries Bioenergetics 4.0 software to examine consumption rates/energy requirements based on variations in biological/physical parameters.
  • Limitations of the software to estimate parameter uncertainty and variability in consumption/daily ration estimates prompted development of a custom age-structured bioenergetics model at the individual and population levels.
  • Model equations and VBA code complete for yellowfin; refinement of variance parameter estimates and equations for active metabolic rate (i.e. estimates of minimum and average swim speeds) continues.
  • Modifications to all model input files complete and sensitivity analyses in progress.
  • Life history data on dolphinfish and skipjack compiled for consumption model development.
Challenges and key lessons learnt
  • Significant challenges were encountered learning the new software and its limitations. As a result, a custom model was required to be built, which has delayed the work, but greatly improved the quality of the analyses.
  • Proposals to conduct gastric evacuation experiments, the sampling for predator/prey caloric values and additional experiments to refine bioenergetics parameters were delayed due to the pandemic.
  • Document SAC-10 INF-E, May 13-17, 2019; Internal summary report of Fisheries Bioenergetics 4.0 modeling simulations to estimate consumption of yellowfin tuna, Thunnus albacares/70th Tuna Conference, May 20-23, 2019
  • A draft manuscript for the scientific journal, Reviews in Fish Biology and Fisheries, will be submitted for review in September 2021.
This project is a critical precursor to experimental work required to estimate values of the consumption/biomass ratio (Q/B) for an ecosystem model in development for the EPO.