Closed structures are evolving. The purpose of floating closed fish cage systems is to preserve the environment around the sites, control the water quality of the water and prevent lice from spreading.

Examples of closed structures are:

• Flexible bags as liceskirts
• Stiffer constructions in plastic, concrete or fiberglass

Closed systems change the physic of the structure. Forcing the water to flow around and underneath the structure, instead of flowing through as for traditional fish nets.