Cages

Cage culture involves placing a mesh or wire cage in a flowing, open water system, such as a lake, stream, reservoir or ocean. Originally, cages were used by fishermen to hold their catch until the fish were ready to sell. The constant water flow is critical as it renews the oxygen supply and removes waste products with little effort by the aquaculturist. The size of mesh used for the cage is critical as it must prevent the entry of predators, while holding the valuable fish stock.

Cage culture is often advantageous because it can be practiced on a small scale in almost any body of water. In addition, cage culture is relatively unobtrusive to the landscape and leaves opportunity for the water to be used in other ways, such as recreational fishing. Unfortunately, the closed, confined environment often leads to the rapid spread of disease in the caged community. Other disadvantages include the possibility of fish escaping into the environment and the cost incurred to feed the fish, as they have less access to natural food sources in the caged structure. Also, cages are vulnerable to damage by pollution, storms and vandalism.

Four different types of cages are common: fixed, floating, submersible and submerged.

Fixed:
A fixed cage is essentially a net bag supported by posts which are anchored to the bottom of a river or lake. Although they are inexpensive, their use is limited to shallow, protected water with soft substrates.

Floating:
Floating cages are made from netting supported by a buoyant collar or a stable frame. This is the most widely used method of cage aquaculture because the cages can be made any size or shape.

Submersible:
These cages are built with a rigid frame and because they are submersible, they can be moved up and down in the water column to take advantage of water conditions. If the weather is rough, the cage is lowered to calmer water, but in calm conditions the cage remains near the surface.

Submerged:
These cages are the least common and are permanently kept under the water. They consist of a frame with slats for openings and are anchored to the substrate in flowing water