Egg incubation and larval rearing of piava, Leporinus obtusidens: effect of pH / Incubação de ovos e larvicultura da piava, Leporinus obtusidens: efeito do pH

ABSTRACT

The aim of this study was to evaluate the effect of the pH of the water during Leporinus obtusidens egg incubation and larval rearing. During incubation of the eggs pH 5.0, 7.0 and 9.0 were tested. pH 7.0 produced the best results for fertilization rate, hatching, and weight of hatched larvae (29.62 ± 6.01%, 23.57 ± 2.81% and 0.63 ± 0.01 mg, respectively). As pH 5.0 caused total mortality of eggs, the pH range was expanded in larval rearing that used pH 5.0, 6.0, 7.0, 8.0 and 9.0. pH 5.0 and 6.0 were lethal to the larvae at 24 and 72 h, respectively. At pH 9.0, higher survival (87.22 ± 3.47%) and final weight (3.82 ± 0.19 mg) were registered, whereas the final length of the larvae was the same (P>0.05) for pH 7.0, 8.0, and 9.0. Incubation at extreme pH values was harmful to the development of the L. obtusidens eggs, while at neutral pH (7.0), the best hatching rate and weight of hatched larvae were obtained. During larval rearing, the acidic pH was lethal to the larvae within just a few hours of exposure, whereas higher larvae survival and final weight were registered at pH 9.0.

RESUMO

O objetivo deste estudo foi avaliar o efeito do pH da água durante a incubação dos ovos e a larvicultura de Leporinus obtusidens. Durante a incubação dos ovos foram testados os pH 5,0, 7,0 e 9,0. Em pH 7,0 foram obtidas as maiores taxas de fertilização e de eclosão e o maior peso das larvas eclodidas (29,62 ± 6,01%, 23,57 ± 2,81% e 0,63 ± 0,01 mg, respectivamente). Como o pH 5,0 causou mortalidade total de ovos, a faixa de pH testada na larvicultura foi ampliada, tendo sido testados os pH 5,0, 6,0, 7,0, 8,0 e 9,0. Os pH 5,0 e 6,0 foram letais para as larvas em 24 e 72 h, respectivamente. Em pH 9,0 foram registrados os maiores valores de sobrevivência (87,22 ± 3,47%) e peso final (3,82 ± 0,19 mg), enquanto o comprimento final das larvas foi o mesmo (P>0,05) em pH 7,0, 8,0 e 9,0. A incubação em valores extremos de pH foi prejudicial ao desenvolvimento dos ovos de L. obtusidens, enquanto em pH neutro (7,0) foram obtidas as maiores taxas de eclosão e peso das larvas eclodidas. Durante a larvicultura, o pH ácido foi letal para as larvas após poucas horas de exposição, enquanto a maior sobrevivência e peso final foram registrados em pH 9,0.