I'd never heard of these systems, so I Googled them. Here's a description from researchers at Virginia Tech:
"Recirculating aquaculture refers to a method of growing fish at high densities under controlled conditions in indoor tanks. This approach to fish production minimizes the amount of water and land needed, and greatly expands the opportunities to grow fish in geographic areas that are normally unsuitable locations for seafood harvesting."Some photos:
- Virginia Tech, Recirculating Aquaculture Technology Is Warding Off Future Seafood Shortages (pdf), 2007
Fish farming sure has gone high-tech.
Right from Process Aquatics International, Downingtown, PA