The reason albacore are worse than light tuna is that the albacore tend to be giffer fish 60-80lbs and therefore higher up in the food chain. Light canned tuna is made from the 5-6 lb variety. Sharks are top of the food chain - large fish - that have higher contaminates. Most fake crab is made from shark (big = bad) or pollock (2lb fish = good)
This idea holds true for all other fish. The larger the fish, the higher up the food chain, the more time they have been around to eat bad things, and the more likely they are to pass it on to you. You can keep safe by eating smaller fish. Sockeye salmon rather than King salmon, etc...
Other weird fish things. Wild salmon have less contaminates than farmed salmon (they hypothesize it is the crappy fish food they feed fish at farms).
There are also some acute problems with local fish in areas that have had heavy mining sediment deposited in local lakes and streams. Where I live entire towns have been labeled as Superfund sites. I only fish is smaller local lakes that didn't have mining activity.
Here is a website with no mercury info but good fish info
http://www.pacseafood.com/products/albacore.html
and here is a website with the lowdown on Mercury
http://www.epa.gov/ost/fishadvice/advice.html, most of which was already quoted above.