Efeitos do pH sobre a incunbação e o desenvolvimento inicial de peixes com diferentes estratégias reprodutivas.

Abstract

Reproduction of fish in a natural environment tends to occur in ideal conditions for offspring survival. Among these conditions the extreme values of pH can affect the initial stages of fish species differently. In this context, this study aimed to evaluate the influence of pH on the survival and early development of two species of fish with different reproductive strategies, Astyanax lacustris (small distance migrant) and Piaractus mesopotamicus (long distance migrator). The experiments were divided into two trials (incubation and larviculture) with five pH levels. The first test was the incubation, by means of a water recirculation system with the aid of incubators made with 2-liter pet bottles. The second test was the larviculture, where three-liter aquaria were used. The pH did not influence the hatching rate of A. lacustris eggs, but affected the diameter of the calf, while the newly hatched larvae presented some skeletal deformities. Piaractus mesopotamicus had a pH effect on hatching rate and perivitelline space, while newly hatched larvae had several skeletal deformities. In A. lacustris larviculture there were no effects on larval survival, but the variables analyzed showed significant differences between treatments. The survival rate of P. mesopotamicus was affected by acid pH and all variables analyzed also varied significantly between treatments. It is concluded that the incubation and larviculture assays of A. lacustris and P. mesopotamicus revealed a significant and differentiated influence of the pH variable on the survival and development of these species.