Karthik R, Angelin C Pushpam, Yashika Chelvan and Vanitha MC
Shrimp farming is one of the most important aquaculture practices worldwide. In general, the excess feed and faecal matter deposited in the bottom of the pond undergo ammonification and result in excess of ammonia formation in pond water and sediment. In addition, eutrophication in the culture system/pond can cause stress to the animals and ultimately end with microbial diseases. The present simulation study was carried out to isolate the potential beneficial bacterial strains to improve the shrimp microbiota (GIT) and to reduce the ammonia and nitrite toxicity in shrimp grows out ponds on a laboratory scale experiment. The Bacillus stratosphericus (AMET1601) isolated from Marine sediment samples, showed strongest antibacterial activity against shrimp pathogens. The Nitrosomonas sp AMETNM01 and Nitrobacter sp AMETNB03 were isolated from shrimp culture pond sediments using Winogradsky Phase I and Phase II medium. A total of 150 shrimps (Litopenaeus vannamei) seeds were obtained from a commercial shrimp hatchery located in Marakanam, Kanchipuram District. The Zoea of Litopenaeus vannamei kept in the experimental tanks was fed with Cheatoceros calcitrans and enriched Artemia salina up to PL20. Then, the average weight of the shrimps were divided into three batches in 100L glass tanks (70L of seawater), each containing 50 post larvae. The Tank 1 was treated with commercial feed and the Tank 2 and 3 were treated through feed supplemented with 105 CFU g-1 of Bacillus stratosphericus (AMET1601) for 40 days. After 30 days of culture, in tank 3 the ammonia and nitrite oxidizing bacterial strains such as, Nitrosomonas sp AMETNM01 and Nitrobacter sp AMETNB03 strains (each in the range of 105ml-1) were added (only once on the 31st day) and the Ammonia (NH4+), Nitrite (NO2) Nitrate (NO3) in the all the tank water were analyzed from 31st day up to 40th day. The shrimp survival (%), Individual Weight (wt/pcs) and the microbial load revealed that the tank 3 (Combination of Bacillus stratosphericus AMET1601, Nitrosomonas sp AMETNM01 and Nitrobacter sp AMETNB03) was found to be superior comparatively in probiotics than other two tanks. The present study suggests that, the use of beneficial bacterial strains in shrimp culture could prevent the aquaculture pond from undergoing eutrophication and control the shrimps from microbial diseases and ultimately enhance the production.
