Effect of salinity on the behavior and oxygen consumption of Mugil curema (Pisces, Mugilidae)

White mullet fingerlings (Mugil curema) occur together with freshwater species, of the Poeciliidae and Characidae, in a pond neighboring the beach at Pontal do Sul (Parana, Brasil). They tolerate changes in water quality during the year, brought about by the action of rains, waves and tides. When acclimating in the laboratory to various salinities, the highest survival rate for Mugil curema fingerlings (2.3 to 9.7 cm) is obtained at 8.5% salinity for temperatures between 13 and 30 degrees C. M. curema fingerlings do not survive in freshwater. The behavior of the individuals and of the group was related to the acclimation salinity in different temperature ranges. The most stressing condition, with highest oxygen consumption, was at 1.7% salinity; the equilibrium point between the internal and the external medium, with the lowest oxygen uptake, per gram fish, in one hour, was recorded at 8.5% salinity.