Effects of Chronic Ammonia Exposure on Growth of Genetically Improved Farmed Tilapia (GIFT) Cultured Under Different Densities

• Published in: North American journal of aquaculture 2023-01, Vol.85 (1), p.21-30
• Main Authors: Sánchez Ortiz, Iván Andrés, Bastos, Rafael Kopschitz Xavier, Lanna, Eduardo Arruda Teixeira
• Format: Article
• Language: English
• ISSN: 1522-2055; 1548-8454
• DOI: 10.1002/naaq.10268

Tilapia are among the most widely cultivated fish species in the world, with a high level of importance for freshwater fish production. An important tilapia variety for the international market is genetically improved farmed tilapia (GIFT; Nile Tilapia Oreochromis niloticus). Multiple studies have been developed to determine the maximum concentrations of ammonia (NH3) recommended for the cultivation of various varieties of tilapia; however, there are no specific data for the cultivation of GIFT. Growth results for GIFT fry exposed to NH3 at 0.50, 0.89, and 1.58 mg/L in 69‐d chronic toxicity tests were evaluated. The experiments were conducted in three recirculation aquaculture systems, one for each concentration of NH3. Stocking densities were 33, 66, and 132 fish/m3. Fish were fed ad libitum three times per day. The only mortalities recorded were for treatments with the highest NH3 concentration (1.58 mg/L), which had a cumulative mortality of 89.5%. There were no significant differences in weight gain for the three stocking densities assessed at an NH3 concentration of 0.50 mg/L. Results indicated that GIFT juveniles can be cultured with stocking densities of up to 132 fish/m3 in environments with ammonia concentrations of up to 0.89 mg/L without compromising fish survival, although the daily weight gain was between 30% and 41% lower than the values reported for optimal culture conditions.