Egg survival and timing of hatch in two Scottish Atlantic salmon stocks

Atlantic salmon eggs from the Rivers Oykel and Shin were monitored in three rivers and in culture. Significant mortality, attributable to low pH, was found for both stocks in the River Oykel though it was eightfold higher for the non‐native Shin eggs. Shin eggs hatched earlier at all three wild sites but hatched later in culture. The observations are consistent with genotype‐environment interactions for pH sensitivity and developmental rate.