I'm fairly smart, but wonder how much more I'd have accomplished if I had gotten a better diet.
I was going to say that your parents probably fed you tuna,
but I looked it up and canned tuna doesn’t count as an oily fish, only fresh tuna.
Anyway, here’s a list of oily fish
https://metro.co.uk/2018/05/01/oily-fish-list-salmon-tuna-mackerel-count-oily-fish-7511476/