Utilization of Sodium Chloride, Formalin and the Association of these Products in the Control of Ectoparasites in Tilapia (Oreochromis niloticus) Larvae

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 cost of products utilization. The experiment was developed in the laboratory of the Instituto de Pesca, Sao Paulo, SP. The larvae were placed in a tank with biological filtration for a period of 24 hours, while it was made a qualitative evolution of parasitism, in 40 animals, and the determinations of frequency occurrence of parasites larvae. Afterwards, they were distributed in 48 aquariums with 20 L of water and continuous aeration, with density of 2.0 larvae L super(-1). The air and water temperature and pH, conductivity, dissolved oxygen, alkalinity, hardness and calcium of the water were monitored. Sixteen treatments with three repetitions each one were used: three with sodium chloride (2.5; 5.0 and 10.0 g L super(-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 2.5g L super(-1) plus formalin 1:40,000 were the most effective, eliminating 100% of the parasites, showing larvae survival rate above 90% and cost of US$ 9.19 100 m super(-3) and US$ 62.14 100 m super(-3), respectively.Original Abstract: O trabalho visou testar a viabilidade da utilizacao do cloreto de sodio, da formalina e da associacao destes produtos na eliminacao de 100% de ectoparasitas de larvas de tilapia-do-nilo (Oreochromis niloticus), considerando os resultados de sobrevivtacia das larvas e o custo de utilizacao dos produtos. O experimento foi desenvolvido nos laboratories do Instituto de Pesca, Sao Paulo, SP. As larvas foram colocadas em caixa de agua, com filtracao biologica, por um periodo de 24 horas, enquanto era realizada, em 40 animais, avaliacao qualitativa da parasitose e a determinacao da frequencia de ocorrencia de larvas parasitadas. Posteriormente, as larvas foram distribuidas em 48 aquarios com 20 L de agua e aeracao constante, na densidade de 2 larvas L super(-1). A temperatura do ar e da agua, o pH, condutividade, oxigenio dissolvido, alcalinidade, dureza e calcio da agua foram monitorados. Foram empregados 16 tratamentos, com tres repeticoes cada um: tres com cloreto de sodio (2,5; 5,0 e 10,0 g L super(-1)), tres com forma