The densities for an open net-pen system are about 15 kilos per cubic metre. For land-based and recirculating aquaculture systems, you're looking at a minimum of about 50 kilos per cubic metre. The primary reason for that is to take advantage of the capital costs, because the difference in capital costs between the two systems is enormous. So you need to be able to maximize your footprint.
On October 27th, 2011. See this statement in context.