Heard about this issue on the radio this morning and wanted to see what was going on. Found this: http://www.csmonitor.com/2005/0608/p02s01-usju.html
which gives some info on current proposals to increase allowed offshore fish farming.
Also found some background on the issue:
I am most concerned about the farm fish escaping and inter-breeding with the wild fish. Numbers of anadromous wild fish species have been declining for years as we have made it harder for them to swim upstream to their spawning grounds. When a farm fish and a wild fish breed, the offspring get the genetic traits of the farm fish, which are ideal for bulking up quickly, and swimming around in a cage. The fish need to have the genetic makeup of a wild fish, which allows them to make runs hundreds of miles upstream, often leaping over waterfalls on the way.