Water quality parameters including dissolved oxygen, temperature, pH, ammonia, and nitrite levels are fundamental determinants of fish welfare in aquaculture systems. Poor water quality causes physiological stress and disease.
Fish in aquaculture cannot escape poor water quality — they are entirely dependent on farmers maintaining appropriate conditions. Physiological stress from suboptimal water quality suppresses immune function, increases susceptibility to disease, and reduces growth. Chronic low-level water quality problems may not cause obvious symptoms but represent ongoing welfare costs. High stocking densities, common in intensive systems, can rapidly deteriorate water quality without adequate filtration and aeration. Good water quality management is therefore a fundamental welfare responsibility.