New tech seen cutting hatchery reliance on wild mangrove crabs

MINDANAO State University’s Iligan Institute of Technology is developing a recirculating aquaculture system to improve hatchery survival rates for mangrove crabs, which is ultimately expected to reduce the reliance on wild-caught crabs for breeding.

The Philippines is a major producer of mangrove crabs (Scylla serrata), supplying both domestic and export markets. However, most hatcheries still rely on wild-caught broodstock, which has raised sustainability concerns.

The system, called SmartRAS provides controlled rearing conditions for immature adult crabs, particularly through temperature regulation and improved water quality management.

According to the research team led by Mercedes M. Pates, conventional broodstock systems typically record survival and spawning rates of below 40%. SmartRAS aims to address this through a polychaete-assisted biofilter that naturally improves and stabilizes water quality.

SmartRAS, developed from a project supported by the Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (PCAARRD), combines the biofilter with optimized temperature control, targeting a significant reduction in stress among broodstock and improved reproductive performance.

Project findings showed higher survival, spawning, and hatching rates in the modified recirculating system compared with conventional broodstock management. The system maintained lower ammonia and nitrite levels, indicating improved water quality.

The project also identified 27 degrees Celsius as the temperature at which broodstock exhibited the highest survival and reproductive performance.

“By compartmentalizing the tank, this modified RAS design effectively reduced cannibalism, a common issue in crab culture, leading to higher survival rates. Larvae produced in the RAS environment were healthier and of better quality compared to those from conventional systems,” PCAARRD said in a statement.

Researchers said the system could help reduce dependence on wild-caught broodstock and support more consistent seed production once development and validation are completed. — Vonn Andrei E. Villamiel