Utilization of sodium chloride, formalin and the association of these products in the control of ectoparasites in tilapia (Oreochromis niloticus) larvae

Abstract

The objective of this study was to test the viability of the use of sodium chloride, formalin and the association of these products in removing 100% of parasite in common tilapia (Oreochromis niloticus) larvae, considering the results of survival of the larvae and the costs of products utilization. The experiment was developed in the laboratory of the Instituto de Pesca, São Paulo, SP. The larvae were placed in a tank with biological filtration for a period of 24 hours, while it was made a qualitative evaluation of parasitism in 40 animals and the determination of frequency occurrence of parasites larvae. Afterwards, they were distributed in 48 aquariums, with 20 L of water and continuous aeration, in a density of 2.0 larvae L^-1. The air and water temperature and pH, conductivity, dissolved oxygen, alkalinity, hardness and calcium were monitored. Sixteen treatments with three repetitions each one were used: three with sodium chloride (2.5; 5.0 and 10.0 g L^-1), three with formalin 40% (1:80,000; 1:60,000 and 1:40,000), nine different associations of salt/formalin, and the control. Initially, 77% of the larvae presented infestation. The treatments formalin 1:40,000 and sodium chloride 2.5 g L^-1 plus formalin 1:40,000 were the most effective, eliminating 100% of the parasites, showing larvae survival rate above 90% and costs of US$ 9.19 x 100 m^-3 and US$ 62.14 x 100 m^-3 respectively.