Maximum Sustainable Yield Assessment in Thailand: A Case of Pelagic Fish in the Andaman Sea

Since 2015, fisheries management scheme in Thailand has been shifted from open access fishery to limited access fishery aiming to reorganize fisheries in and outside Thai waters with the views to prevent IUU fishing and to preserve aquatic animal resources as a sustainable source of food for humanity. Based on the Royal Ordinance on Fisheries B.E. 2558 (2019), fishing license is issued based on reference point. Currently, maximum sustainable yield (MSY) is used as the reference point for fishing license issuance. The MSY assessment is conducted every year with three groups of species, i.e. demersal fish, pelagic fish, and anchovy, due to the complexity of tropical multi-species fishery. Then, the total allowable catch (TAC) is determined based on the MSY assessment results. The TAC will be allocated to every single vessel both artisanal and commercial fishing vessels and an amount of TAC is specified in commercial fishing licenses.

 MSY assessment of pelagic fish includes several pelagic species, e.g. mackerels, sardines, and scads, as well as neritic tunas. Fox surplus production model is used for the assessment. Catch and fishing effort data between 1998 and 2018 was used for the MSY assessment of pelagic fish in the Andaman Sea in 2019. Thai purse seine was used as the standard fishing gear. The results revealed that the MSY was 118,467 tons at the fishing effort (F_msy) of 68,545 days. While, the catch in 2018 was 119,557 tons with the fishing effort of 45,957 days. In the Andaman Sea, the pelagic resources are now being fished at a fishing effort level commensurate with the F_msy.

In addition, Thompson and Bell model was used to monitor the status of some single pelagic species. Length frequency data of three selected species, i.e., Rastrelliger brachysoma; short mackerel, R. kanagurta; Indian mackerel, and Sardinella gibbosa; goldstripe sardinella in 2018 were used with the model. The results disclosed that F-factor were 1.4, 0.6, and 1.5 respectively indicating that current fishing effort of short mackerel and goldstripe sardinella were lower than its fishing effort level which could produce MSY (F_msy) by 40% and 50% respectively while current fishing effort of Indian mackerel was over its F_msy by 40%. However, length frequency data of neritic tunas were not used with the model due to they are transboundary species and length data obtained was considered not covering the whole stock