Re: Fish Oil
This is what I know from one source but many others agree:
Researchers who tested cans, both oil and water types, reported that they all contained mercury levels higher than the recommended EPA limits for safe consumption. White, or Albacore tuna, registers the highest mercury concentrations.
If you still want to eat tuna, personally I would think the water variety would be a safer bet, but you might want to consider not eating too much of it.
I'm sure others will advise you differently but mercury is one thing I try to be aware of and stay away from. I think you said you also eat salmon, which I think is an excellent choice.