Several factors must be taken into account when choosing a fish cage. Often, the most important considerations for most fish farming operations are the design and the associated cost of each type of cage. The correct type of netting and the size of the mesh are also vital in the construction of an aquaculture cage.
For small fisheries, especially those operating in shallow water, a fixed aquaculture cage is commonly the most economic option. These cages are usually made of net that has been stretched around posts to form an enclosure. The net and the posts are often extended several feet above water line to prevent the fish from escaping.
Floating cages are also mainly comprised of net and thus often reasonably priced. This type of aquaculture cage is designed to move with water currents and can withstand most lake and river conditions with minimal wear and tear. These fish cages are often supported by buoy systems and may be extended or reduced in size with relative ease.
The possibility of extreme weather should be considered when choosing an aquaculture cage. High waves and winds can damage cages that rely on buoys and post anchoring. As these conditions are common in marine aquaculture, fish cages used in oceans are generally submerged or submergible. These cages are usually the most expensive option because the use of metal frames and netting is generally necessary.
Although the use of netting is largely predetermined by the design of a fish cage, certain conditions warrant the use of an alternative material. In areas where predators may have access to the fish, an aquaculture cage may require metal caging to protect against loss. The species of fish held may also require consideration as some breeds are notorious for their ability to shred through even the toughest nylon netting.
Local laws may also affect the choice of cage material. Some areas have banned the use of metal cages due to possible ecological damage from the oxidation of the metals. Some areas have additionally banned certain types of netting. In particular, the use of nylon netting that has been treated with chemicals to prevent the adhesion of fish waste is often illegal.
The size of the holes within the netting is also important. Spaces should be large enough to allow the free flow of water but small enough to prevent escapes. Although many fisheries tend to err on the side of caution by choosing smaller mesh, many professionals advise against this practice. The offal of larger fish can often become lodged in fine mesh, restricting water flow and, consequently, resulting in dangerously low oxygen levels.