Management of multispecies resources and multi-gear fisheries: The case of oceanic tuna fisheries in Vietnam

Abstract

The collapse of many marine fisheries is widely believed to result from mismanagement, which typically focuses on managing a single target species. The objective of this study is to assess the optimal management strategy for multispecies resources and multi-gear fisheries, with a specific application to oceanic tuna fisheries in Vietnam. We utilize the Monte Carlo method (CMSY) and Bayesian State-Space (BSM) approach to evaluate the stock status of skipjack tuna (SKJ) (Katsuwonus pelamis), yellowfin tuna (YFT) (Thunnus albacares), and bigeye tuna (BET) (Thunnus obesus) in Vietnam’s sea waters. Additionally, we establish reference points for tuna fisheries by utilizing bioeconomic models and tuna fishing data from longlines (LL), gillnets (GN), and purse seines (PS) for the period of 2000–2019. The findings reveal that SKJ and YFT stocks are overexploited, while the BET stock is not overfished in Vietnam’s sea waters, even though there have been warnings of overfishing in the Western and Central Pacific Ocean. The tuna fishing effort has exceeded sustainable fishing effort, and the current effort of PS and GN fisheries should be reduced to attain optimal stock and harvest levels. It is also necessary to implement policies that shift fisheries from the current unsustainable situation to a situation where fishing effort corresponds to the reference points. This paper offers a useful foundation for devising a suitable management plan for the sustainable management of tuna fisheries, particularly for non-members of the regional fisheries management organizations.