I gave ds1 strawberries before he was one and I feed him canned tuna. He was probably about 1 the first time he had it. I am just careful not to give him more then 2 servings of it a week, (okay, so we probably only have it once a month...) because of possible murcry levels. I only use the tuna that is packed in water.
i didn't realize that strawberries were an allergen, and just gave them to my 8mo last week. it was one of the few times i've given him commercial baby food (we were out of town for my FIL's funeral and it was easier), and the jar said 6 months+. it was pears, strawberries, and bananas, and he LOVES bananas and pears, so i got it and gave it to him, and then DH comes in and says, "strawberries. wow. those are an allergen." then MIL pops up with, "yeah, i'm very allergic to them." :oops
but DS was fine -- no red butt, nothing. and he loved it.
Info on fish/sustainability/mercury levels can be found here in case you are interested. We eat a lot of fish and are very carefully about what DS eats so it is worth checking out the site - :gvibes