Issues of Exploitation of Sharks by Thai Commercial Fisheries in the Andaman Sea

Abstract

The decline of sharks from the world's oceans has been widely recognized as a major environmental concern by the international conservation communities. This problem is particularly severe in the Southeast Asia region, especially Thailand, which is reported as one of the countries with the greatest declines of shark catches and is now in serious need of management measures. Unfortunately, scientific information concerning this taxon in this region is scarce, presenting a major hindrance to the development of conservation and management strategies. To address this shortage of information, market surveys at major shark landing sites of Thai commercial fisheries in the Andaman Sea were conducted over an entire year in Ranong province of Thailand, after a decade in which the massive declines in the shark catches (>90%) were recorded. In this study, catch composition, landing patterns and biological information of each shark species presented at landing sites were recorded. Of the 64 species previously reported in the existing Thai species list of sharks in the Andaman Sea, only 17 species were observed in this survey, although 1 genetically-confirmed new species, and 2 undescribed species were also recorded. In terms of species diversity, sharks from the family Carcharhinidae were the most diverse group, being represented by 11 species in this study. By number, the landings were largely dominated by bamboo sharks Chioloscyllium spp. from the family Hemiscylliidae, which contributed c. 65% of the total landings, followed by requiem sharks from the family Carcharhinidae, which contributed c. 30.5% total landings. By biomass, the landings were likewise dominated by carcharhinids, which contributed c. 71% to the total landings, followed by hemiscylliids, which contributed c. 27% to the total landings. The other sharks, which comprised single species from the families Squalidae, Sphyrnidae, Stegostomatidae and Triakidae, contributed c. 45% and c. 2% to the remaining percentages by number and biomass respectively. The study also found that the landing composition is markedly different from that reported by the previous landing survey of 2004, with significant declines of most large shark species with slow life-history characteristics, especially sphyrnid and carcharhinid species, which are likely to be at higher risks than most other species. Moreover, the absence of many species from the landings, coupled with noticeable shifts in life-stage compositions of landed specimens that include larger proportions of juveniles and neonates also suggest that the population of these groups of concern may be close to collapse. Management measures which highlight the urgent need for additional fisheries monitoring efforts and an increase in taxonomic resolution and the requirement of scientific research are urgently required. This is especially critical for analysis of the life-history and spatial ecology of key economic species to conduct accurate stock assessment. This thesis suggests that effective management of shark fisheries in the Andaman Sea needs greater incentives from stakeholder parties to encourage stakeholder buy-in of sustainable practices. Effective stock management may require collaborations with other countries in this region for transboundary management of vagile species. In addition, biological information of each shark species recorded is a key priority, which should prove to be beneficial for additional biological research of this group in the future.