Approaches to Stock Enhancement in Mangrove-Associated Crab Fisheries

Abstract

Over the last decade, hatchery production of mud crabs has become technically and economically more feasible, enabling evaluation of the potential effectiveness of hatchery release in fisheries enhancement. The high growth rates and limited movement of released crabs mean that fisheries' yields in isolated mangrove systems with restricted recruitment can be enhanced within a few months. Thus, a release program may be an effective strategy for short-term enhancement in carefully selected specific areas. To date, results are very promising, with recovery rates up to 50% and increases in fisheries' yield up to 46% over baseline catches. In contrast, mark-recapture studies in more open mangrove system populations show that recruitment success and subsequent stock abundance may be largely determined by habitat availability. For these populations, restoration of lost or degraded mangrove areas has been shown to be effective in promoting stock recovery through natural recruitment, with replanted mangroves supporting fisheries of equivalent economic value to that of natural mangroves, though it may take some years to reach these levels. Thus, a balanced approach to stock management could integrate both hatchery-release and habitat restoration programs, depending on local conditions and over different time scales, with parallel co-management to support effectiveness.

Keywords:

• mangrove
• mud crabs
• Scylla
• enhancement
• hatchery
• replanting

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the support of the European Commission through INCO DC contracts ERB-IC18-CT97-0189 and ECA4-CT-2001-10022. They are also appreciative of the constructive comments of two anonymous reviewers.