Application of the Ecosystem-Based Fisheries Resource Assessment Approach for Bigeye tuna (Thunnus obesus)

Abstract

This study is focused on applying an ecosystem-based fisheries assessment (EBFA) approach for the management of bigeye tuna in Fiji’s EEZ. The method involves the application of four main objectives including sustainability, biodiversity, habitat quality and socio-economic benefit. This thesis uses a Tier 2 Approach due to the availability of data and it involves the application of various attributes as well as applying four indicators for sustainability, three indicators for biodiversity, four indicators for habitat quality and five indicators for socio-economic benefit. Each indicator was assigned with a level of magnitude that reflects the importance of the relative indicator. The target and limit reference points was chosen for each indicator to assess the status of species, fisheries and ecosystem. The target reference point relates to a state of each indicator that is considered desirable while the limit reference point is considered as the limit beyond which the state of each indicator is not considered desirable. In utilizing the ‘Tier 2 Approach’, species are given a status for each indicator to denote risk and the mean risk scores for each indicator is directly calculated and estimated from interviews or questionnaire data. Nested risk indices such as the objectives risk index (ORI) and the species risk index (SRI) were also evaluated as they characterize and assess the status of the ecosystem at the management unit level. Problems caused by the various aspect of tuna fisheries can be solved by an ecosystem approach to fisheries management such as this EBFA approach, especially in Fiji’s tuna longline fishery to help reduce high-risk indices in the exploitation of the marine resources.