Regional stock assessment

Stock assessments of the major targeted tuna species in the western and central Pacific Ocean are undertaken periodically by the Oceanic Fisheries Programme (OFP) of the Secretariat of the Pacific Community in collaboration with scientists participating in the Standing Committee on Tuna and Billfish (SCTB). Assessments have been, or will soon be completed for South Pacific albacore (Thunnus alalunga), bigeye (Thunnus obesus), skipjack (Katsuwonus pelamis) and yellowfin (Thunnus albacares) tunas.     [More...]

Development of tuna movement and simulation models

Tuna movement is recognised as playing a major role in population dynamics and in determining the extent of actual and potential interaction between fisheries. A model initially developed from skipjack tagging datasets has been gradually parameterized based on habitat-driven (forage index, SST) movement behaviour, and incorporated with some success in a regional simulation model. This first version of the model has been used to simulate the distribution of skipjack population and catch under climatological (average) conditions. Comparison of CPUE estimated by the simulations with observed average CPUEs have been very promising. A first attempt, here also very encouraging, has been made with a time series of environmental data. The series was however too short and did not cover periods with strong El-Nino/La-Nina conditions to get enough contrast in the data. A longer series should be available in the near future. A thorough parameterisation of the model is also needed and has been started. It will be conducted by fitting the model to catch and effort observations (first on climatological data, then on a time series basis).

Efforts have also continued, in collaboration with the Pelagic Fisheries Research Program of the University of Hawaii, to develop diffusion/advection/reaction models for application to skipjack and yellowfin movement as represented by results from the SSAP and RTTP tagging experiments.

Bioeconomic Modelling of Western Pacific Tuna Fisheries

While substantial progress has been made over the past five years in estimating the various biological parameters of exploited tuna stocks in the western Pacific, the wider issue of the optimal level of fishing has received less attention. Some of the population models that have been developed can now be used as the basis of bioeconomic models which will address the issue of the optimal amount of purse seine and other effort from an economic standpoint. A three-year project, funded by the Australian Centre for International Agricultural Research (ACIAR), and a collaborative effort among the University of Queensland (UQ), SPC and FFA has addressed this issue. The overall goal of the project was to integrate the available information on the population biology of major tuna species in the western Pacific with economic information on the fisheries and markets to provide advice to FFA member countries on optimal (from a bioeconomic point of view) levels of fishing effort.

To this end, a version of the simulation model described above has been adapted to include information on prices and costs, allowing the calculation, at various levels of fishing effort, of the economic rent (total profit of the fishery) and of the economic benefits acruing to FFA countries of the region (based on fees from DWFN and profit from domestic fleets). Two kinds of analysis have been conducted: i) simulations of the effect of changes in the structure of effort on the profits made by each component of the fishery. ii) optimisations determining the structure of effort maximizing an objective function (total rent or FFA profits).

National Fisheries Assessments (Country Reports)

National Fisheries Assessments (NFAs) are produced by the OFP to inform member countries of the status of their tuna fisheries and the stocks that support them. Reports include sections on the biology of the major tuna species, oceanographic influences in the EEZ, reviews of the fisheries and analyses of data, assessment of stocks and management recommendations, where requested. In some cases, the reports have included analyses of RTTP and/or in-country tagging project data, enabling more quantitative assessments and management advice.

Following the recruitment to the Research Scientist position in December 1996, six country reports, for Tonga, Cook Islands, Marshall Islands, Mariana Islands (including Guam and the CNMI), Nauru and Niue have been presented and finalized. NFAs in the near future are expected to involve Vanuatu, Wallis and Futuna and Tuvalu.

Scientific input has also been provided in the development of tuna management plans in Papua New Guinea, Solomon Islands and Palau. During 2000-2001, scientific assistance will be provided for management plans under development in Vanuatu, Fiji, Kiribati and the Cook Islands.

The OFP has also been commissioned to produce resource profiles for five PINs by the South Pacific Project Facility.

Data quality and editing of the tag-recapture database

The OFP’s tagging databases consist of more than 300,000 releases and approximately 26,000 recoveries. This large amount of data continues to be supplemented by long-term tag recoveries, some now nearly 8 years at liberty, and represents a valuable source of information for stock assessment and tuna research. A detailed summary of the RTTP tagging data was recently published in the OFP Technical Report series (Kaltongga 1998). The quality and accessibility of this database continues to be enhanced, with a database query application under development. A large amount of historical Japanese tagging data is also being prepared for use in an integrated skipjack model.

Considerable effort is also expended to reconcile logsheet and observer data, with over 260 trips and 3600 sets matched.

Reporting and Liaison

The reporting and liaison function of the OFP ensures that (i) member country requirements are adequately catered for by the work of the Programme; (ii) the results of OFP research are communicated in appropriate form to member countries; and (iii) member countries receive the best available scientific advice regarding the management of their tuna fisheries. Much of this is achieved through informal contact between OFP staff and Fisheries Officers during country visits, regional meetings, etc, and through formal presentation of work at meetings such as this.
Results of OFP work were reported to member countries at several levels - in broad outline to regional meetings (CRGA, FFC), and in greater detail to the Standing Committee on Tuna and Billfish, now operating under revised terms of reference and incorporating species-based research groups.
Reporting is also provided to specific countries in the form of national assessments (see above), and responses to specific queries on current status of stocks, likely effects of different harvest strategies, etc. Technical input to regional review processes, eg. the Annual Consultation on the US Multilateral Treaty on Fisheries, and to sub-regional bodies, notably the FFC species working groups Statistical reporting occurred at formal publication level (SPC Regional Tuna Bulletin and Tuna Fishery Yearbook) and directly to countries on receipt of data (see earlier).
At the request of the First Multilateral High-Level Conference on South Pacific Tuna Fisheries, the OFP convened and hosted the Technical Consultation on the Collection and Exchange of Fisheries Data, Tuna Research and Stock Assessment (July 1996) and A workshop on the Precautionary Reference points (May, 1998).
Regular liaison is maintained with other regional and international organisations, particularly the FFA, but also the US National Marine Fisheries Service, the Western Pacific Regional Fishery Management Council, the Inter-American Tropical Tuna Commission, the International Commission for the Conservation of Atlantic Tunas, the Indian Ocean Tuna Commission, the Food and Agriculture Organization, the Japan National Research Institute of Far Seas Fisheries, the National Taiwan University, OFDC, the Research Institute of Marine Fisheries (Indonesia), the Bureau of Fisheries and Aquatic Resources (Philippines), and organisations in Australia and New Zealand, to promote collaborative research and exchange of information.