Successful stock enhancement of a lagoon prawn fishery at Rekawa, Sri Lanka using cultured post-larvae of penaeid shrimp

Rekawa Lagoon, Sri Lanka (area 250 ha) has an artisanal fishery for penaeid shrimp, predominantly Penaeus indicus (93.6% of catch), but with small num bers (0.8%) of Penaeus monodon. Neither species breeds in the lagoon; larva e and post-larvae enter the lagoon: during brief periods in July and Novemb er (P. indicus) or just November (Pen. monodon) when a sand bar blocking th e lagoon entrance is breached. Detailed information on fishery characterist ics was collected during the fishing season of 1995-1996. The P. indicus fi shery began in October, peaked in February and was over by late April/early May; while Pen. monodon was only caught from March to early May. The fishe ry was extremely intensive, removing virtually all shrimp by early May. In the light of these data, two stock enhancement exercises were carried out w ith Pen. monodon post-larvae in July 1996 (55,000 post-larvae) and July 199 7 (70,000 post-larvae). These led subsequently to commercial catches of Pen . monodon from September to January (roughly 6 months out of phase with the natural fishery) in both years. Total catch in 1996-1997 represented 3.5% of the number of post-larvae released. In 1996-1997, the total shrimp catch was worth 33% more than in 1995-1996, while the annual Pen. monodon catch was enhanced by 1400%. Economic analysis and scenario modelling were used t o evaluate the biological and economic feasibility of more intensive stock enhancement. This study represents an ecologically and economically sustain able penaeid stock enhancement approach by which shrimp aquaculture and art isanal fishing can cc-exist. (C) 1999 Elsevier Science B.V. All rights rese rved.