Another place to get that much needed omega 3 is from salmon. Salmon is another great source of lean protein too and it is less likely to carry the same risk of high mercury as tuna.
The other reason that omega 3 is so beneficial is that it can help to alter the balance of omega 3 to omega 6. Omega 6 is found in much of our modern diet and is responsible for increasing blood pressure when we eat it in high quantities. Fortunately, the body always maintains a balance of omega 3 and 6, so that when we get more of one, we automatically lower the other.
Salmon is also a good source of potassium!