The world shrimp aquaculture, has faced several problems, causing severe losses in shrimp hatcheries; between the most critical has been diseases such as early mortality syndrome (EMS) caused by (Vibrio parahaemolyticus). The EMS was initially detected in Asian countries; after, it was disseminated to Mexico and other countries. In Mexico, EMS caused severe economic losses during 2013-2016; and it has not yet been eradicated. Various causes for EMS have been reported; none is entirely accurate, but water quality is essential for successful shrimp aquaculture; therefore, the aim this work was evaluate the ammonia concentration effect on susceptibility to (EMS) on post-larvae (PL-15) shrimp (Litopenaeus vannamei) infected with (V. parahaemolyticus), using a biofilm system (water with, microalgae, dinoflagellates, protozoa and other planktonic microorganisms). So series of 5 flasks each one were arranged as following: Series S; 900 ml of filtered seawater (FSW) and 10 PL-15 shrimp per flask. Series SB; 840 ml of FSW, 60 ml of biofilm and 10 PL-15 shrimp. Series E; 900 ml of FSW, infected with 2 ml (V. parahaemolyticus) 106 CFU/ ml and 10 PL-15 shrimp. Series EN; fifteen flasks with 900 ml of FSW, 10 PL-15 shrimp, added with NH4Cl (0.535 mg/ml), to get 0.5, 1.0, 1.5, 2.0 and 2.5 mg/l final ammonia concentration in 5 sub-series of 3 flasks each one. During experiment, ammonia concentration and PL-15 shrimp mortality were evaluated in all flask. Ammonia concentration was higher in series EN than in series E; the same was observed in Series S respect to SB, but at lower values. At end of experiment, mortality in series EN was 90% Vs 60% in E. Similarly, mortality in series S was 10% Vs 0% in SB. This results confirm that the ammonia increases PL shrimp mortality, and biofilm system reduce ammonia and consequently PL-15 shrimp mortality.
Selection of Bacillus spp. isolates having enzyme producing ability and antagonistic to Vibrio parahaemolyticus causing the early mortality syndrome (EMS) on shrimp
