Effects of Water Preparation Systems on Microbial Dynamics and AHPND Severity in Litopenaeus vannamei Culture

The Pacific white shrimp (Litopenaeus vannamei) is a major species in global aquaculture, but its production is constrained by bacterial diseases such as Acute Hepatopancreatic Necrosis Disease (AHPND). This field study evaluated the effects of different water preparation and management systems on microbial dynamics, water quality, disease severity, and production performance in commercial shrimp farms along the Persian Gulf coast of Iran. Five farming systems were compared: traditional reservoir filtration (T۱), mechanical drum filtration (T۲), lined ponds without reservoir (T۳), earthen ponds (T۴), and small lined ponds with intermediate storage and chlorination (T۵). The results showed significant differences among treatments. T۲ and T۵ exhibited lower Vibrio and total heterotrophic bacterial loads, improved dissolved oxygen levels, and reduced ammonia and nitrite concentrations. In contrast, T۴ showed the highest bacterial densities, poorest water quality, and lowest shrimp survival (۲۵%), whereas T۵ achieved the highest survival rate (۸۰%). PCR analysis confirmed the presence of pirA and pirB toxin genes of Vibrio parahaemolyticus across all systems; however, disease severity varied depending on environmental conditions. These findings indicate that pathogen presence alone does not determine AHPND outcomes, and that microbial control and environmental stability are critical determinants of disease severity. Integrated water treatment strategies, including mechanical filtration, sedimentation–disinfection reservoirs, and lined pond systems, were associated with reduced microbial loads and improved production performance. Overall, effective water preparation and biosecure management are essential for mitigating AHPND and enhancing sustainability in intensive shrimp farming systems.

کلیدواژه ها:

Litopenaeus vannamei ، AHPND ، water treatment systems ، microbial dynamics ، shrimp aquaculture ، biosecurity.