Omega 3 and omege 6 fatty acids are both essential fot the body to function well.
Omega 3 fatty acids found in cold water fishes such as sardines and salmons, fish oils, cod liver oil and flax seed oil. Omega 6 fatty acids are found in corn oil, sun flower oil, soy oil, peanut oil , meats, and dairy.
Now the body needs a health balance of omega 3 and 6 fatty acids to function.
Omega 6 fatty acids promote inflammation within the body . This tells the body that it needs to come to that area of the body and repair it for proper healing.
Omega 3 fatty acids acts to reduces (inflammation) in the blood vessels and prevents the blood cells (platelets) from clumping together. It helps to stop the blood from clotting, decreasing the risk for strokes or heart attacks

Too much omega 6 fatty acids can cause too much inflammation for too long a period and lead to a chronic inflammation state which can lead to blood vessel disorders and harmful effects on the organs in the body.
Too much omega 3 fatty acids can increase the risk of bleeding within the body.
So a healthy balance of the fatty acids need to be reached.
Now Sardines, even if canned, are a rich source of omega 3 fatty acids. Cannned sardines can come packed in water, oil or a sauce. Try using the sardines which are packed in water, preferably without salt. Now in the Mediterranean they sometimes pack their sardines in olive oil, which has a mixture of omega 6 and 3 fatty acids.
The debate is still on about the exact balance of omega 6 and 3 fatty acids needed in the diet.
So just make sure to get the high quality sardines packed in water.