Effect of tilapia polyculture on quantity of suspended particulate matter and Vibrio in Litopenaeus vannamei rearing enclosure

We conducted an experiment on the polyculture of Litopenaeus vannamei. GILI tilapiahad been cultured in 24 enclosures in a pond located at Dianbai, Maoming City, Guangdong Province from June to August, 2011. We set 6 treatments with 4 replicates each, and a single enclosure was a replicate. Each enclosure was stocked with 3 000 shrimp seeds. Treatments A, B, C, D and E were polycultured with 4, 8, 12, 18 and 24 juvenile GILI tilapia after 28-day shrimp seeding, while the other 4 enclosures without tilapia were set as the control group F. Quantity of suspended particulate matter and Vibrio in polyculture enclosures were observed periodicallyso as to analyze theeffect of tilapia polyculture on the quantity of suspended particulate matter and Vibrio in L.vannamei rearing enclosure. The results show that: 1) The content of total particular matter (TPM), particular organic matter (POM), particular inorganic matter (PIM), POM/TPM and PIM/TPM were identical among treatments at earlier culture stage; at the mid and later stage, POM/TPM, the contents of TPM and PIM were higherin experimental groups than in the control, while PIM/TPM was higher in the control than in experimental groups;PIM /TPMs in group C, group D and group E were higher than in Group A and Group B. 2)At later stage, the Vibrio quantity ranged from 1.01103 CFUmL-1 to 152.33103 CFUmL-1, average (15.0824.50) 103 CFUmL-1. The quantity of Vibrio was the highest in Group A, followed by Group B, Group C and Group D. These results indicat that under the shrimp-tilapia polyculture model with big tilapia fries, when the initial stocking ratio of shrimp to tilapia was about 250:1, the sediment organic matter accumulation and over reproduction of Vibrio could be decreased effectively, which can improve environment and economic benefit.