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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.
