Modified mangrove pens for polyculture system in mud crab (Scylla serrata) and milkfish (Chanos chanos) production

The mangrove pens were modified to produce mud crab (Scylla serrata) and milkfish (Chanos chanos) in a polyculture system. The modification of mangrove pens was done by adding excavations inside the pen. The water quality parameters (dissolved oxygen (DO), pH, salinity, and temperature) were monitored, and the recovery and production rates in each pen were evaluated. The experiment was conducted for a rearing period of 143 days in nine mangrove pens, each having an area of 32 m2 and an average net enclosure height of 3 m from the soil surface. The three different pens constructed (existing design: canal only, 43% excavation by area, and 54% excavation by area) were designated as T1, T2, and T3, respectively. The water quality parameters recorded in the pens were favorable for the growth and recovery of the mud crab and milkfish, except for DO. For mud crab, the highest mean recovery was recorded in T2, followed by T3, and the lowest in T1. The production rate followed the same pattern as the recovery, with T2 having the highest, followed by T3, and T1 having the lowest. The statistical analysis revealed that the variations in mud crab recovery were not significant, while in terms of production rate, modified mangrove pens were found to be more effective than the existing design. Due to the total mortality of the cultured milkfish, the current set-up of modified mangrove pens was found to be unsuitable for the polyculture system of milkfish and mud crab production.