When selecting the sites for sea cage farms several criteria are important. Some species independent criteria used when evaluating a site are as follows:
1. Stable water quality (the actual quality requirements will be species dependent)
2. Good water exchange, but not too high a velocity (below 1 m/s is recommended)
3. Minimum depth under the cages of 5 m
4. Good infrastructure
5. Temperature above 0°C to avoid icing; otherwise temperature appropriate for the species
6. Not close to potential sources of water contamination
7. For wave heights above 3 m the equipment costs are rather high.
When having a sea cage farm the use of several sites is recommended. If having species that need more than one year to reach the marked size or when having several inputs of juveniles every year it is advisable to use different sites (Fig. 21.26) to reduce the possibility of disease transfer between the inputs/generations. In addition, is it advisable to let the sites rest for a year after some years in production. This has been shown to improve production on the site. If this production model is used, the sites must not be too close together. The distance depends on the current conditions between the sites, but typically at least 1.5 km is recommended.