Aquaculture Crsp 22nd Annual Technical Report

An experiment was conducted over a period of 150 days at Can Tho, Vietnam to adapt integrated cage-cum-pond systems to local conditions in Vietnam, to determine appropriate stocking density of selected fish species in cages, to assess growth and production of fishes in both cages and open ponds, and to assess the economic and environmental benefits of this integrated system. Nile tilapia (Oreochromis niloticus) fingerlings (10.1 g) were stocked at 2 fish m-2 in all ponds of 100-m2 area, while climbing perch (Anabas testudineus) fingerlings (9.0 g size) were stocked in a 4-m3 cage suspended in each pond. Stocking density of Anabas was the treatment variable and was 50, 100, 150, and 200 fish m-3, giving caged climbing perch to open-pond Nile tilapia ratios of 1:1, 2:1, 3:1, and 4:1. There were also control ponds without a cage (0:1), and control ponds were fertilized weekly with urea and diammonium phosphate (DAP) at 28 kg N and 7 kg P ha-1 week-1. Pelleted feed (26–28% crude protein) was given to caged fish twice daily at a rate of 5–2% body weight per day. No fertilizer was added into treatment ponds. Survival of climbing perch in cages ranged from 97.1% to 99.6%, without significant difference among treatments. Mean weight of climbing perch at harvest was not significantly different among treatments, indicating that stocking density of climbing perch in cages did not affect growth. Net and gross yields were significantly higher in the treatments at higher stocking ratios. FCRs were very high in all treatments, ranging from 4.97 to 6.07. Survival and growth of Nile tilapia did not differ significantly among treatments. Combined net and gross yields ranged from 3.0 to 6.6 and 4.0 to 8.7 t ha-1 year-1, respectively, in the treatments. Overall FCRs ranged from 0.98 to 1.58, which, however, did not differ among treatments. The highly valued climbing perch has potential to be cultured in a cagecum-pond culture system, but it is necessary to fine-tune stocking ratios, provide high quality feed, and improve growth of Anabas.