Published online by Cambridge University Press: 16 December 2014
Through the experiments presented here we wanted to test whether egg production of theblack-chinned tilapia Sarotherodon melanotheron heudelotii underexperimental conditions varies as a function of ambient salinity (fresh waters vs.sea waters vs. hypersaline waters, 0, 35 and 70, respectively)and whether these responses differ between fish acclimated within a few weeks from freshwater to saline and hypersaline environments (experiments E1 and E2, monitoring over 10and 18 weeks), and individuals born and raised all life long at the experimentalsalinities (E3, monitoring over 18 weeks). In total, 233 spawns were collected. In each ofthe three experiments, the reproductive investment (gram of egg per gram of female over 2weeks) did not differ between salinities of 0 and 35, whereas it was 2–3 times lower at 70than at 0–35, because of lower spawning frequency (E1-E3), smaller clutch size (E1) andlower spawn mass (E1-E3). Finally, fish acclimated to salinity from fresh water over a fewweeks and those maintained at a particular salinity all life long showed similarreproductive traits, thereby emphasizing the remarkable physiological plasticity of thisspecies.