We found similar urea-N/(urea-N + TAN) ratios to those published. Kaushik (1980)
found 14% in rainbow trout, while GuCrin-Ancey (1976) found between 10 and 20% in
sea bass, depending on temperature and food intake. This was mostly due to the changes
in ammonia excretion, resulting directly from feed intake, rather than to changes in urea
excretion. The differences noticed in urea production between 10 and 100 g fish weight
classes may reflect the overall metabolism of the fish rather than the effect of feeding
level.