An intensive land-based recirculating aquaculture system (RAS) is designed for rearing Atlantic salmon (Salmo salar). The system recirculates marine water from the rearing tank, through a mechanical drum filter, a trickling biofilter, and a seaweed (Saccharina latissima) bioremediation channel, before returning the cleansed water to the salmon.
State the primary chemical form in which nitrogenous metabolic waste is excreted across the gills of teleost fish.
Explain why a failure in the mechanical drum filter, leading to an accumulation of solid organic waste (faeces and uneaten feed) in the rearing tank, would cause a rapid decline in dissolved oxygen concentration.
Many modern RAS units integrate ozone (O3O_3O3) injection systems into the water sterilization loop. Explain how ozone treatment helps to maintain a healthy salmon population.
Describe the biological processes by which saprobiotic (decomposer) and nitrifying bacteria in the trickling biofilter convert organic nitrogenous waste into a form that can be assimilated by the seaweed to support its growth.
Suggest one management practice salmon farmers use to prevent intraspecific competition and cannibalism within the rearing tank.
