Design marine protected areas (MPAs) for sea cucumbers In the Coastal waters of Sri Lanka

Abstract

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This study attempts to design MPAs to manage sea cucumbers in the coastal waters of Sri Lanka. A bio-economic model developed by Stefansson and Rosenberg (2005) was used in this study. In model simulation, area between 080170 - 060 500 N and 810 250 - 820 was considered and this area was assumed to form 5 x 5 rectangular grids. As population densities varied with depth, five vertical rectangles were assigned to represent depth categories; 0-5m, 5-10m, 10-15m, 15-20m, 20-25m. Initial biomass was set at 87 tons and historical fishing mortality was; Fhist = Fcrash where Fcrash = r = 0.4. The base model was run for 50 years before the onset of management to get internally consistent population structure. This model was simulated under different biological assumptions to understand the changes in biomass within next 15 years. Biomass recovery rate within and outside the MPAs is related to the larval dispersal rate. Biomass changes in depth categories were simulated under 90% larval dispersal rate and 6 contiguous closures. Prediction showed that biomass in deeper depths start to increase after 2-4 years, but it takes more than 10 years in shallow depths. Three times increase in current yield can be expected at the end of 15 years. Biomass fluctuations within and outside the MPAs were predicted under different closures and the highest biomass within MPAs can be expected when 15 contiguous rectangles are closed. Spatial management through MPAs is seen to have potential to rebuild the depleted sea cucumber populations.