I don't think I know a single person who's never eaten fish nor I think it is possible at all.
Even if you think you do, fish is actually added to a very large amount of processed food even if it has nothing do to with fish at all.
Worchester sauce, salad dressing, protein bars, gummy candies, margarins, anything that contains omega 3, vitamins and an infinitely larger amount of fish and fish oil/paste is added to virtually anything you can find in the supermarket.
Pork-derived collagen is the industry standard when it comes to clarification (e.g. people don't like to see wine that isn't transparent and has no sediments) so they are surprised there's pork used in a gargantuan amount of food. Same happens with fish.
It's extremely unlikely people haven't eaten fish, even if they don't know it.
If you go to a sushi place you're eating farmed fish 100%, if you have eaten some salmon roll, you're eating farmed fish.