In addition to salinity, other factors such as low or high pH, high concentrations of
environmental ammonia, and exposure to air affect resting ammonia excretion. However,
many studies of environmental influences on nitrogen excretion by fish involved extreme
conditions, and most studies have considered short-term rather than long-term
consequences of environmental variables (Wood, 1993, 2001). Comparing the effect of
salinity on different species has been hindered because of variation in experimental design
and conditions among previous studies.