Status of demersal fishery resources in the Gulf of Thailand

Data from trawl surveys (1961 - 95) and annual production statistics (1971 - 95) were used to examine the status of demersal fishery resources in the Gulf of Thailand. Analyses were focused on biomass trends, population parameters and exploitation rates of dominant species, and assessment of excess capacity from fishing effort and yield estimates. The results indicate by 1995, the trawlable biomass in the Gulf had declined to only about 8.2% of the biomass level in 1961. The substantial decline is true for major components (demersal fish and trash fish) and species groups (Nemipterus spp., Priacanthus spp., Saurida spp. and squids) comprising trawlable biomass. Estimates of exploitation rate (E) for 23 species indicate that most (particularly demersals) are over-fished. By 1995, 21 of the species had E values of 0.79 and higher. Analyses of standardized fishing effort and yield using the Fox model indicate that the 1995 fishing effort was about twice the level needed to harvest the maximum sustainable yield. Overall, the results illustrate that the resources are severely over-exploited. The excess demersal fishing effort is estimated to be about 50% of the number of registered boats in 1995.Fishery resources, Demersal fisherie, Fishery surveys, Biomass, Population density, Shrimp fisheries, Catch/effort, ISEW, Thailand Gulf,

Preliminary analysis of demersal fish assemblages in coastal waters of the Gulf of Thailand

The 1995 trawl data of the research vessels Pramong 2 and 9 in the Gulf of Thailand were analyzed using TWINSPAN and DCA. Four main station clusters were identified related to geographic location and depth. Two clusters are associated with shallow water areas and the other two clusters are found in deeper areas with water depths > 30 m. Temporal analysis indicates clustering of monthly data into wet and dry seasons. Examination of species abundance data indicates that the seasonality may not be very pronounced. However, this may be due to the degree of disaggregation used in sorting the trawl survey samples.Fishery resources, Demersal fisheries, Fishery surveys, Biomass, Population density, Shrimp fisheries, Catch/effort, Trawling, Population characteristics, ISEW, Thailand Gulf,

Assessment, Management and Future Directions for Coastal Fisheries in Asian Countries

Abstract The biomass of 40 ecological groups, the diet composition of prey and predators, production/biomass (P/B) and consumption/biomass (Q/B) ratios, and catches were used as basic input to parameterize an Ecopath model of the Gulf of Thailand. Following construction of a mass-balance ecosystem model, a time-dynamic simulation model (Ecosim) was used to simulate the impact of change in fishing effort. This was done using time series data to validate the historic fisheries development in the Gulf of Thailand prior to using the model for forward-looking simulations. The time series data used in the analyses were catch and effort data from research vessel trawl surveys and landings data for six groups of fishing gear operating in the Gulf during the period 1973 to 1993. The fish market price and fixed and variable costs of each fleet (as well as profit) were also used as input for the time-series simulations using Ecosim. The results depict changes in biomass and trophic interactions in time (Ecosim) and space (Ecospace). The model was also used to investigate management options or measures for the fisheries of the Gulf of Thailand. Recommendations for future studies using Ecopath with Ecosim are also presented