Aquaculture Systems Overview

Types of Aquaculture

• Different types of aquaculture exist based on hydrobiological features, the motive of farming, and special operational techniques.

Open Aquaculture Systems (OASs)

• OASs involve rearing aquatic organisms within enclosed systems in natural environments like freshwater rivers, coastal marine regions, and brackish estuaries.
• They utilize floating mesh cages anchored to the seafloor.
• Examples of organisms cultured in OASs include seabream, seabass, codfish, tilapia, salmon, and shark catfish.
• Cultured species in OASs rely on a fishmeal diet.
• Stick, rack, and rope-based OASs are used to culture mussels and oysters, which are filter-feeders and do not require fishmeal diets.

Demerits of OASs

• Require fishmeal for feeding carnivorous species, leading to poor conversion ratios (e.g., 5kg of fishmeal is required to breed 1kg of fish).
• High fish densities increase disease and parasite transmission.
• Risk of fish escape and interbreeding with wild populations.
• Accumulation of fecal waste reduces water quality.
• Disposal of sticks and racks can be a concern in some areas.

Closed Aquaculture Systems (CASs)

• CASs involve land-based breeding of aquatic organisms in ponds, raceways, and tanks.
• They maintain a controlled interface between the reared species and the natural environment.
• Implement sophisticated waste management procedures that filter generated wastewater and cycle it back into the aquaculture system.
• Recirculating aquaculture systems are a typical example of a CAS.
• Species reared in CASs include Atlantic salmon, Cobia, Catfish, Tilapia, and European bass.

Key Elements of a CAS

• Monitoring: Continuous monitoring of water quality and fish health.
• Fish Handling: Proper handling and management of fish populations.
• Feeding: Artificial diets typically consist of fishmeal and fertilizers.
• Filtration Unit: Removes particulate matter and acts as a biofilter.
• Temperature Control: Water heating systems are sometimes required depending on water temperature and fish species.
• Aeration Unit: Provides dissolved oxygen for the fish.
• Ozone/Ultraviolet Sterilization: Reduces bacterial and organic loads in the water.

Advantages of CASs

• Maintain water quality due to negligible interference with natural waterways.
• Employ sophisticated waste management procedures.
• Prevent fish escape to surrounding waters.
• Reduce transmission of fish diseases and parasites.
• Improve fish quality and growth rates.
• Enhance food conversion efficiency.
• Reduce dependency on therapeutic treatments.