Quantification of nitrogenous excretion of fish is important for fish transportation,
intensive fish culture operations, and closed recirculating systems. Before stocking fish in
recirculation systems, the capacity of the biological filter should be adequate to remove
nitrogenous wastes because of the high toxicity of ammonia. Consideration of the effects
of salinity and other variables on ammonia and urea excretion is important for proper
design of fish transport and culture systems, both to avoid toxicity and to maximize
efficiency.