Aquaculture involves the production of a diversity of aquatic species reared in a variety of production environments. The animals are reared in fresh, brakish and sea water, in warm water or cold water, in closed systems like recirculation aquatic systems, semi-open systems, like ponds and raceways, or in open systems, like cages or net pens. In closed or semi-closed systems, part of the wastes may be recovered using simple or more elaborate approaches.

These animals consume compound feeds formulated to different nutritional specifications using a variety of feed ingredients and feed manufacturing techniques. The composition of the feeds and how well the animals use the feeds determine the amount of waste released by the animals, whether fecal wastes or dissolved wastes, such as ammonia, phosphates, carbon dioxide, etc.

These wastes can have negative effects on the receiving environment, either by stimulating eutrophication or by causing localised deleterious or toxic conditions (such as high ammonia or localised hypoxia).

Several factors affect the fate of the waste released by the animals and their effects on animals and the environment. For example, ammonia toxicity is very much a function of the pH of the water but also of temperature and salinity. Some wastes have no discernable effects on the receiving environment whereas limited amounts of certain wastes can have significant effects on the environment.

Delineating the fate and effects of wastes in an aquatic environment is very complex. There is a need for technological approaches and tools that would allow us to better reduce or manage waste outputs and predict its fate and effects under different production systems and environmental conditions encountered in aquaculture production.

• How might we better manage animal waste output and predict its effects in different aquaculture production environments?