Salinidade da água durante a masculinização de Tilápia do nilo (Oreochromis niloticus) em sistema de bioflocos

Abstract

The aim of the present study was to evaluate water salinity for Nile tilapia (Oreochromis niloticus) in bioflocs during masculinization. Seven salinity levels (0, 2, 4, 6, 8, 10 and 12 g/L) were tested in tilapia after absorption of the yolk sac, for four weeks (masculinization period), in a matured bioflocs. There was no difference between treatments for temperature, dissolved oxygen, settleable solids, total suspended solids and nitrate. Total ammonia was bigger than 1 mg/L for almost all treatments, however, the averages of toxic ammonia remained below the toxicity threshold. The pH, alkalinity and nitrite variables increased with higher salinity levels. The nitrite peaks were bigger for the higher salinities too, in addition to a significant negative correlation with the survival rate. Final biomass and feed conversion demonstrated a reduction and an increase, respectively, with the increase in salinity. The survival rate decreased with the increase of salinity and the masculinization rate tends to reduce too. Therefore, salinity should be kept close to 0 g/L in the masculinization protocol of Nile tilapia larvae in BFT, for a better survival, food conversion ratio and to guarantee higher masculinization rate.