The site you linked to about mercury in seafood is actually maintained by the fishing industry which has an interest in getting people to eat more fish by not informing them about the true dangers of mercury.
A better and more balanced resource is the free on-line mercury in seafood calculator at Sea Turtle Restoration Project?:?Got Mercury?. Based on government guidelines and information, it's a more accurate and objective calculator.
The government has issued a warning a to women and children to not eat swordfish, shark, tilefish and king mackarel and limit their consumption of tuna. New scientific studies show that tuna accounts for 37 percent of the mercury in the diets of Americans. The Got Mercury calculator can help people make more informed decisions when it comes to which fish is safer to eat.