Stock and Fishery Dynamics of Yellowfin Tuna, Thunnus albacares, in the Western and Central Pacific Ocean: Development of an Integrated Model Incorporating Size and Spatial Structure

PDF file of Hampton and Fournier reprint, "A spatially-disaggregated, length-based, age-structured population model of yellowfin tuna (Thunnus albacares) in the western and central Pacific Ocean", John Hampton and David Fournier, Marine Freshwater Resources, 52: 937-963, 2001

Updated MULTIFAN-CL based assessment of yellowfin tuna, a Working Paper presented at SCTB 13, July 5-12 2000, Noumea. (PDF file from SPC-OFP web site, 1.1 MB)

Progress Report - June 1997

In late 1993, a small group of scientists from the Western Pacific Yellowfin Research Group (WPYRG) examined the prospects for developing an integrated model of yellowfin dynamics, incorporating both size and spatial structure. A modelling strategy, building on the length-based assessment model (MULTIFAN CL) applied to South Pacific albacore, was developed. The key extension of MULTIFAN CL envisaged was that spatial structure, initially in the form of the 7 WPYRG areas, would be incorporated into the model. Inputs to the proposed model would include total catch and effort data, length frequency samples and tagging data, all variously stratified by gear, fleet, area and time period. The University of Hawaii PFRP has provided funding for two-year project to coordinated by the Oceanic Fisheries Programme of the South Pacific Commission.

1996-97 Activities

Work has continued on the development of MULTIFAN CL, mainly through application to the albacore data from the SPC's Albacore Research Project. Key model developments incorporated in the past year include:

• the inclusion of age-dependent natural mortality
• the incorporation of tagging data as auxiliary information into the model

1997-98 Work plan

Due to technical difficulties associated with model development, particularly the incorporation of tagging data into the analysis, and a delay in the provision of year 2 funding to the 1997-98 FY, we have fallen somewhat behind schedule in the application of the model to yellowfin data. However, we expect to finalize the application of MULTIFAN CL to yellowfin in 1997-98, subject to receipt of project funding. We will focus on the following activities:

(a) Continue to enhance the model, in particular to:

• Develop a two-dimensional movement sub-model that includes advective as well as diffusive components.
• Formally incorporate multiple cohorts per year into the model.
• Continue to develop auxiliary data handling by the model. The two types auxiliary data that will be incorporated for the yellowfin analyses are tagging data and age-length data. SPC has a large yellowfin tagging database that provides information on movement and mortality. SPC also has a project to age yellowfin directly from otoliths. This data set will provide important information on mean length at age.

(b) Obtain at least a preliminary "best fit" to the yellowfin data, which can then be used to investigate relevant management questions.

(c) Fully document the model and its application to western and central Pacific yellowfin.

This page updated August 16, 2006