Description

Abstract: This experiment was conducted in nine 200m2 earthen ponds at the Asian Institute ef Technology, Thailand for 133 days from 21 May to 2 October 2003, to investigate effects of adding shrimp (Penaeus monodon) into” intensive Nile tilapia (Oreochromis niloticus) ponds on the growth performance, water quality and nutrient utilization efficiency in different stocking combinations of tilapia shrimp polyculture. There were three treatments in triplicate each: tilapia at 11m2 and shrimp at 151m2 (low tilapia density), tilapia at 21m2 and shrimp at 151m2(medium tilapia density), tilapia at 41m2 and shrimp at 151m2 (high tilapia density).

Mean daily weight gains and final mean weight of tilapia in the low tilapia density treatment was significantly greater than those in the medium and high tilapia density treatments, between which there was no significant difference. However, total weight gain, and net and gross yields of tilapia were highest in the high tilapia density treatment, intermediate in the medium tilapia density treatment, and lowest in the low tilapia density treatment. Final mean weight of shrimp was not significantly different among all treatments, however, survival and net and gross “yields in the high tilapia” density treatment were significantly poorer than those in the medium and low tilapia density treatments, between which therewere no significant differences.

Nutrients incorporated by Nile tilapia biomass accounted far 48.01%, 52.89%, and 48.99% of TN, and 60.55%, 68.47% and 62.25% of TP inputted from fertilizer and pelleted feeds in the low, medium and high tilapia density treatments, respectively, while shrimp recovered only 1.10% and 0.33% of TN, and 0.55% and 0.27% of TP in the low and medium tilapia density treatments. However, nutrients were lost through deaq shrimps in the high tilapia density treatment. Overall mean DO concentrations at both surface and bottom were highest in the low tilapia density treatment, intermediate in the medium and lowest in the high tilapia density treatment. Overall mean concentrations of TAN tended to be higher at higher tilapia density.

The present experiment indicated that adding shrimp into Nile tilapia ponds is technically feasible, however, more research is needed to optimize the tilapia-shrimp polyculture system.