I don't believe high salinity killed it. Fish can tolerate high salinity much easier than low salinity, especially if it rises gradually.
Ron Shimek's Website...Critters
Coral reefs are generally located in areas that have salinities in the range of 35 ppt (1.026) to 38 ppt (1.028 SG
). Most of our corals, and the associated fauna including fishes, will live best at those conditions (Weber and White 1976). Most organisms, even osmoconformers, can survive for brief periods in salinities well outside their normal range. But if maintained for longer period outside of that range they will be stressed and eventually will become so damaged that they will die even if returned to their normal salinity. Higher salinity is slightly more tolerable to these animals than is lower salinity,
and adult animals are more able to withstand the extremes than are the juveniles or larvae.
Incidentally, the Red Sea is a noteworthy exception to the above generalization regarding salinity in reef situations. The southern Red Sea averages about 38-40ppt (1.030 SG
), the central Red Sea averages about 40-41 ppt (1.031 SG
), and the northern Red Sea has salinities up to 41-42 ppt (Kleypas, et al., 1999). These salinities approach the upper survivability limit of salinity which is about 42 ppt (1.032 SG
), which is reached in some hypersaline lagoons.