Abstract

Overfishing causes a significant decline in blue swimming crab (Portunus pelagicus) populations, an essential marine resource for Thailand. This research aimed to identify suitable nursery areas for this species throughout the four distinct monsoon seasons. This is the first comprehensive study of habitat characteristics: water temperature, pH, salinity, dissolved oxygen, marine sediment, seagrass beds, and suitability assessment of nursery areas, using a combined approach of Analytic Hierarchy Process and Geographic Information Systems. Our findings reveal that highly suitable nursery habitats comprise a small percentage of the total study area, varying with the monsoon season: 1.66% in the Northeast Monsoon (NEMS), 1.00% in the NEMS transition (NEMST), 1.11% in the Southwest Monsoon (SWMS), and 1.97% in the SWMS transition (SWMST). These areas are concentrated along the coastlines of Sed Island, Phum Riang, Takrob, Tha Thong, and Donsak. Sed Island was designated as a fishery refuge zone in 2022. The identified nursery areas coincide with existing crab banks, highlighting the model's accuracy. Conversely, unsuitable areas were predominantly in shellfish farming zones and low-salinity estuaries. By identifying suitable nursery grounds for the blue swimming crab, this study offers valuable information that can support Thailand's sustainable management and conservation efforts for this species.