Pacific white shrimp (Litopenaeus vannamei) dominates global shrimp aquaculture, making up the largest share of farmed shrimp (FAO, 2022), and its rapid expansion has been driven by the increasing global market and the development of high-density intensive culture systems. However, intensification has led to major water-quality challenges, particularly the buildup of total ammonia nitrogen (TAN-N) and nitrite (NO2-N), both of which are highly toxic to shrimp. Although toxicity thresholds have been established for ammonia and nitrogen individually, shrimp in commercial systems are often exposed to both compounds simultaneously, and their potential interactive and combined effects remain poorly defined. Therefore, the present study aims to quantify the combined effects of TAN and nitrite on the survival and growth performance of L.vannamei to develop more practical and relevant water quality thresholds for intensive shrimp aquaculture.
A 30-day trial was conducted on juvenile Pacific white shrimp (initial average weight 1.94 ± 0.2 g). A total of 360 shrimps were placed in 18 aquaria (60L each, 20 shrimp per aquarium), and six different treatments were applied: T1 control; T2 nitrite only (10mg/L); T3 (2mg/L) and T5 (5mg/L) ammonia only; T4 (2,10) and T6 (5,10) mg/L for ammonia and nitrite, respectively. Water parameters were measured, such as temperature 24-27°C, pH 7.5-8.2, dissolved oxygen 5.5-6.5 mg/L, and salinity at 20 ppt. Ammonia-N, nitrite-N, and nitrate-N were measured twice a week. Nitrite levels were raised to 20mg/L and subsequently to 30mg/L after mortality was not observed at 10 mg/L.
After 30 days, survival and growth of Pacific white shrimp differed significantly across treatments (p <0.05). The lowest survival and growth occurred in treatments combining ammonia and nitrite (Table 1).