Studying the status of culturing techniques and the estimation of the ability to assimilate organic carbon, nitrogen and phosphorus from feed in intensive white leg shrimp (Litopenaeus vannamei Boone, 1931) ponds in Bac Lieu province

Abstract

Bac Lieu is one of the largest brackish shrimp farming provinces in the Mekong River Delta. An analysis of the current status of white shrimp farming in Bac Lieu Province has been conducted based on a questionnaire. The study results showed that most households cultured one (accounting for 26%) or two crops per year (accounting for 71%), and stocked shrimp in earthen ponds was 91%. The stocking time was from January to March (83% of total farms), the average culture time was 97.7±16.5 days/crop. The area of   ponds ranged from 0.2-0.4 ha/pond (76%), and the most designed pond area was 0.3 ha/pond, accounting for 22%. The stocking density concentrated in two main density groups of 5060 individuals/m2 and 80-100 individuals/m2 with small size (PL10-PL15). Commonly used feeds were Grobest, Cargill and CP with an average FCR of 1.27±0.09, and shrimp were fed 4 times a day (72%). The survival rate of shrimp was 83.8±10.6%, the shrimp size was 62±16 shrimps/kg, and the yield was 10.2±3.38 tons/ha/crop. In addition, the feed samples and the shrimp samples (stocking and harvesting) were collected to study the assimilation of organic carbon, nitrogen and phosphorus from the feed in shrimp ponds. These indicators were analysed according to Boyd & Tucker (1992), TCVN 1525:2001, and Kieldahl methods. Sampling results showed that the assimilation of organic carbon, nitrogen and phosphorus from the feed in shrimp was rather low and significantly different among stocking densities.