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Modelling the effects of climate change
Impacts of climate change on tuna
Friday, 18 February 2011 10:43

Background

The tuna fishery in the western and central Pacific Ocean (WCPO) has undergone continuous expansion over the past 30 years, with the catch of skipjack, yellowfin, bigeye and albacore tunas reaching 2.4 million tonnes in 2007. The landed value of the catch in 2007 was approximately USD 4 billion, with considerable economic benefits accruing to Pacific Island Countries and Territories through direct participation in the fishery, employment, onshore processing, provision of fleet services and support, and foreign access licence fees.

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Project purpose
Friday, 18 February 2011 11:35

The purpose of the project is to provide advice to SPC members on the likely changes in tuna stocks that will occur as a result of climate change during the 21st century, by building on and extending the model development and applications already undertaken.

The project is structured in two phases.

Phase 1 would complete the preliminary evaluation of the climate change effects on the four main tuna species of importance in the SPC region, i.e. skipjack, bigeye, yellowfin and albacore tuna, under the IPCC A2 scenario. It would also conduct simulations under the IPCC B1 (reduced emissions) scenario for comparative purposes. This is currently being funded by the Australian Department of Climate Change and Energy Efficiency, and should be completed in the second half of 2011.

Phase 2 would undertake a more comprehensive suite of analyses of the four species to characterize the uncertainty in the predictions in relation to alternative population dynamics model structures, parameter uncertainty and plausible climate change scenarios. This would be a major research effort involving considerable computer and human resources. SPC is actively seeking funding support for this phase of the project.

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Historical work
Friday, 18 February 2011 11:29

In 1995, the SPC Oceanic Fisheries Programme (OFP) initiated the development of a Spatial Ecosystem and Population Dynamics Model (SEAPODYM), in which tuna stock distribution and abundance is modelled in relation to the biological characteristics of the stock and their interaction with environmental conditions (e.g., water temperature, currents, oxygen concentration, primary productivity, etc). The objective of this work was to better understand the impact of oceanographic variability, in particular that associated with ENSO, on tuna stocks and fisheries. The development of the model has continued at SPC, in collaboration with the University of Hawaii Pelagic Fisheries Research Program, and more recently, with Collecte Localisation Satellites (CLS), a subsidiary of the French CNES and IFREMER institutes. The current version of the model has reached a high degree of sophistication, with the main features being (i) forcing by environmental data (either observed or modelled); (ii) prediction of the temporal and spatial distribution of age-structured tuna populations; (iii) prediction of the total catch and size frequency of the catch by fishing fleet; and (iv) parameter optimization based on fishing data assimilation techniques. The model has been extensively described and published in the peer-reviewed scientific literature.

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Preliminary outputs
Friday, 18 February 2011 13:58

Lehodey P., Senina I., Sibert J., Bopp L, Calmettes B., Hampton J., Murtugudde R. (2010). Preliminary forecasts of population trends for Pacific bigeye tuna under the A2 IPCC scenario. Progress in Oceanography. 86: 302–315. 

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Project activities
Friday, 18 February 2011 11:40

Phase 1 activities:  Preliminary evaluation of the climate change effects on the four main tuna species of importance in the SPC region

  • Revise/complete the parameter optimization for Pacific skipjack, bigeye, yellowfin and South Pacific albacore tuna populations using the forcing fields of the ORCA-PISCES coupled model forced by the atmospheric NCEP reanalysis (previous skipjack and bigeye optimizations were undertaken with the ESSIC reanalysis). This revision to the earlier optimizations is required for consistency with the Earth system modelling framework now generally used for climate change simulations.
  • Produce preliminary estimates of the climate change impacts through the 21st century on Pacific skipjack, bigeye, yellowfin and South Pacific albacore tuna populations under the IPCC A2 and B1 (reduced emissions) scenarios. Reporting of model outputs will cover the 21st century, with particular focus on 2035 and 2100 to be consistent with IPCC reporting protocols and the 5th IPCC Assessment Report in particular.
  • Document the methodology and results of the research for peer-reviewed scientific publication.
  • Use the results of the modeling to inform the more general debate on climate change impacts on Pacific fisheries and aquaculture, including vulnerability assessments, implications of impacts and possible adaptation strategies.
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Schedule
Friday, 18 February 2011 11:53

The main resources required for the project would be human (scientific) and computer resources. The scientific work of Phase 1 would be carried out largely through a contract to CLS to provide the planned modelling.

For Phase 2, a specialist three-year post at SPC would be required, as well as computer, travel and other support. For both phases, the SPC OFP would provide supporting scientific inputs, particularly in the areas of fishery data compilation for SEAPODYM models, model interpretation and publication.

 


 
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