Currently, there is a very strong debate in British Columbia regarding land-based salmon farms: if this technology exists, why isn’t the industry adopting it? On-land recirculation systems separate farmed salmon from the natural environment, thus removing any potentially harmful environmental effects that may stem from open net-cages. Wastes from the farmed fish can be collected and treated rather than being released into the marine ecosystem. Additionally, any diseases or parasites can be screened for and monitored much more closely, thus protecting both the farmed stock as well as the wild fauna.
However, there are several key points that must be addressed in this debate. The first is that land-based systems are extremely expensive, both to build and to operate. By their very nature, a land-based recirculation system is much more capital-intensive to set up than a net-pen operation: tanks, pipes, pumps, filters, the land itself, a building if necessary...these are all costs that net-pen operations do not have to cope with. Add into the equation the cost of electricity and the overall carbon footprint of the facility, and suddenly land-based systems are not looking as attractive.
There is a fantastic report by Fisheries and Oceans Canada (2010) that states that while land-based recirculation systems may be economically viable, their high operating costs make them extremely sensitive to fluctuations in market conditions (the price of salmon, the price of electricity/water, etc.): the margins are so small that a tiny shift in the market may be all that is necessary for the system to lose its profitability.
That report is available here: http://www.dfo-mpo.gc.ca/aquaculture/lib-bib/nasapi-inpasa/BC-aquaculture-CB-eng.htm#7
While it may not be possible for the salmon industry in BC to adopt these systems immediately, there is hope on the horizon. As I write this, researchers and engineers are working hard to continue developing these technologies with the sole purpose of increasing efficiency and decreasing operating costs. Additionally, by implementing other sustainable farming methods (aquaponics, solar/wind power, etc.) the operating costs can be reduced even further.
It is my opinion that these systems are inherently better than the current practices, but unfortunately we are simply not yet prepared to adopt them.