As a result, aquaculture and fish-farming, which involve the rearing of fish from the larval stages to the adult stage in confined/closed conditions, is increasing too since fish populations in the wild are decreasing.

The captive fish (e.g. in large nets out at sea) are fed continuously and this may result in pollution of the seabed directly under the fish cages (since not all the food given is eaten by the fish), which may become anoxic with time.