Sensitivity of fish eggs to acid stress

Craig & Baksi ( Water Res. 11, 621–626, 1977) may have exaggerated the effect of acid stress on oogenesis by comparing the low viability of eggs laid and incubated at pH 4.5 and 5.0 with the higher survival of eggs laid at pH 6.7 and transferred after 12 h to pH 4.5 and 5.0. On the basis of our findings, a lower survival would have been observed in the latter group if the eggs had been transferred immediately to the acid conditions. The egg changes its character rapidly after being laid. Permeability decreases and the chorion hardens during the first few hours after release, allowing the egg to become more resistant with time. The results of two experiments are reported to demonstrate this effect.