Effects of interaction between pH and stocking density on the growth, haematological and biochemical responses of Nile tilapia juveniles

This study evaluated the interaction between pH and stocking density on growth performance and biochemical and physiological variables in Nile tilapia juveniles. Nile tilapia exemplars were subjected to low (0.63 kg m−3, LSD), medium (1.26 kg m−3, MSD) and high stocking density (2.52 kg m−3, HSD) at three different pH levels (5.74, 7.14 and 8.62) for 60 days. Un-ionized ammonia was higher at the alkaline pH. Alkalinity was higher in the HSD than the LSD treatment. The fish exposed to HSD presented lower growth performance. Exposure to acidic pH and HSD promoted the highest plasma cortisol levels. Plasma glucose levels were higher at acidic pH and MSD. Mean corpuscular haemoglobin showed maximum values under exposure to alkaline pH and LSD. Leukocyte count was lower at acidic pH and HSD. Heterophiles showed maximum values in fish subjected to circumneutral pH and MSD. In conclusion, circumneutral pH and MSD were the best conditions for Nile tilapia production systems.