Read the whole article here: http://www.sciencealert.com.au/news/20100103-20657-2.html
"Farmed tuna dodge mercury"
New research has found that mercury levels in farmed tuna’s are much lower than those in the wild. This is GREAT news. During farming the fish are fed more than a wild tuna would consume so that they fatten up much faster than their wild companions. It looks like it is due to this process that they contain less mercury, due to the “rapid growth rate.” It is also due to the fact that the tuna are fed bait-fish that have lower levels of mercury themselves. This might be the news that helps push farming as a more sustainable and attractive option. It seems to me that if the current ban that has been proposed does not work, then this might be the next best option.