Total ammonia nitrogen in tank-water samples from Norway (Fig. 4A and B) shows very variable concentrations. Juvenile tank samples (Fig. 4B) were significantly higher than smolt tank samples (Fig. 4A) (904 576 and 438 440 mg N/L, respectively). The resulting calculated ammonia (mg NH3/L) values were 0.81 0.90 and 0.62 1.13, respectively. CO2 levels were not significantly different between smolt (11.4 6.2) and juvenile (12.8 6.4 mg/L) tank samples (Fig. 4C and D, respectively). Similar data sets are currently not available for Chile.