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111
Stocking Densities for Tilapia-Shrimp Polyculture In Thailand

Tenth Work Plan, New Aquaculture Systems/New Species Research 3B (10NSR3B)
Final Report

Yang Yi, Wanwisa Saelee and Potjanee Naditrom
Aquaculture and Aquatic Resources Management
Asian Institute of Technology
Pathum Thani, Thailand

Kevin Fitzsimmons
Environmental Research Lab
University of Arizona
Tucson, Arizona, USA

Abstract

This study, consisting of two experiments, was carried out at the Asian Institute of Technology (AIT), Thailand, to determine optimal conditions for stocking and rearing Nile tilapia (Oreochromis niloticus) and tiger shrimp (Penaeus monodon) in a polyculture system at low salinity. Both experiments were conducted in nine 200 m2 earthen ponds with three treatments in triplicate each: shrimp alone at 30 per m2 (monoculture, control); shrimp at 30 per m2 and Nile tilapia at 0.25 per m2 (low tilapia density polyculture); shrimp at 30 per m2 and Nile tilapia at 0.50 per m2 (high tilapia density polyculture). In experiment one, the feed ration was varied and determined daily by feeding-tray method in every pond during the 65-day culture period, while the fixed same feed ration for all ponds was determined by a feeding table during a 75-day culture period in experiment two.

In experiment one with varied feed rations, the growth, yield and survival of shrimps was not significantly different among all treatments. Although the Food Conversion Ratio (FCR) (1.62–2.24) of shrimps were not significantly different among all treatments, shrimp monoculture had significantly lower feed input than tilapia-shrimp polyculture. However, in experiment two with fixed feed rations, the low tilapia density polyculture resulted in significantly higher shrimp yield than the monoculture and high tilapia density polyculture. FCR of 1.44 in the low tilapia density polyculture was significantly better than those
(1.73 and 1.69) in both monoculture and high tilapia density polyculture, respectively.

In both experiments, Nile tilapia showed fast growth (3.98–4.70 g per fish per day). There was no significant difference in growth and survival of Nile tilapia between the low and high tilapia density polyculture, while fish yields were significantly higher in the high tilapia density polyculture than those in the low tilapia density polyculture.

Partial budget analyses indicated that under varied feed input (experiment one), the highest net return was achieved in the shrimp monoculture, intermediate in the high tilapia density polyculture, and lowest in the low tilapia density polyculture, while under the fixed feed input (experiment two) the low tilapia density polyculture gave the highest net return, followed by the high tilapia density polyculture and shrimp monoculture. Under varied feed input, the added cost produced negative added return in the low tilapia density polyculture, and the ratio of added return to added cost in the high tilapia density polyculture was 0.73. However, under fixed feed input, the ratio of added return to added cost in the low tilapia density polyculture reached 22.69, which is higher than that (5.04) in the high tilapia density polyculture.

The present study indicated that the addition of Nile tilapia into shrimp ponds can improve feed utilization efficiency, resulting in better economic returns and less environmental pollution. The present study showed that the tilapia-shrimp polyculture with appropriate feeding strategy is technically feasible, economically attractive, and environmentally friendly.

Introduction

In Thailand, intensive culture of black tiger shrimp (Penaeus monodon) has developed rapidly along the coastal area since 1987. Thailand has been the world’s leading marine
shrimp producer since 1991 (Fast and Menasveta, 2000). One of the major problems for Thai shrimp farmers in coastal areas is disease outbreaks (such as white spot) that often cause the failure of marine shrimp production. The success of shrimp culture at low salinity led to a rapid ex