Ammonia Toxicity to Chinook Salmon Parr: Reduction in Saline Water

Abstract The acute toxicity of un-ionized ammonia (NH3) to parr of chinook salmon Oncorhynchus tshawytscha in fresh water and in water of four different salinities was determined in 24-hour static tests. The 24-hour median lethal concentration (LC50) in fresh water was 0.36 mg NH3/liter. The LC50 at a salinity of 9.6‰ was considerably higher (2.2 mg NH3/liter). Lower LC50 values, indicating greater toxicity, were obtained in water of both lesser and greater salinity. Reduction of ammonia toxicity is a major benefit of brackish-water culture of chinook salmon. Received February 8, 1982 Accepted August 5, 1983