Through the experiments presented here we wanted to test whether egg production of the
black-chinned tilapia Sarotherodon melanotheron heudelotii under
experimental 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 fresh
water to saline and hypersaline environments (experiments E1 and E2, monitoring over 10
and 18 weeks), and individuals born and raised all life long at the experimental
salinities (E3, monitoring over 18 weeks). In total, 233 spawns were collected. In each of
the three experiments, the reproductive investment (gram of egg per gram of female over 2
weeks) did not differ between salinities of 0 and 35, whereas it was 2–3 times lower at 70
than at 0–35, because of lower spawning frequency (E1-E3), smaller clutch size (E1) and
lower spawn mass (E1-E3). Finally, fish acclimated to salinity from fresh water over a few
weeks and those maintained at a particular salinity all life long showed similar
reproductive traits, thereby emphasizing the remarkable physiological plasticity of this
species.