Influence of Temperature and Salinity Acclimation on Temperature Preferenda of the Euryhaline Fish Tilapia nilotica

Abstract

When Tilapia nilotica was acclimated to temperatures of 15–35 C and salinities of 0–30‰ in a vertical gradient tank, maximum temperature preferenda occurred at acclimation temperatures of 20 and 25 irrespective of salinity. Preferenda declined as acclimation temperature was increased above 25 C and, except at 0 and 7.5‰, declined as acclimation temperature was decreased below 20 C. The pattern of the relation between final temperature preferenda and salinity was similar to that reported between oxygen consumption for a given sustained swimming speed and salinity. The final preferendum was lowest at 15‰, close to the isosmotic salinity of T. nilotica, and highest at the extremes, 0 and 30‰. Final temperature preferenda are in general agreement with optimum temperatures reported for growth, reproduction, and swimming performance.