Nitrate bioaccumulation, growth performance and survival of rainbow trout ( Oncorhynchus mykiss ) in aquaponics with elevated water NO ₃ -N levels

Aquaponics systems offer a sustainable method for the combined production of fish and plants, but they may lead to elevated nitrogenous compounds in water to satisfy plant nitrogen requirements. However, limited information is available on nitrate accumulation in fish flesh under increased nitrate nitrogen (NO3-N) conditions. This study assessed the performance of rainbow trout reared in an aquaponics system exposed to NO3-N levels exceeding optimal thresholds. Although water NO3-N concentrations surpassed recommended values, nitrate levels in fish flesh remained low and within acceptable food safety limits. Muscle nitrate content peaked when water nitrate concentrations approached their highest levels (approximately 135 mg/L NO3-N) and subsequently declined. Rainbow trout survival remained high even at elevated NO3-N concentrations; however, growth performance was reduced, likely due to prolonged exposure to high nitrate levels. These findings indicate that rainbow trout cultured in aquaponics systems remained below established food safety limits, even under conditions of increased nitrate concentrations in the rearing water.