Mentioning previous answers is just intended to help with faster answers, but is not intended to discourage further questions or discussion.

It was discussed a few days ago in /u/mikedash's reply to the now deleted "Did Late Age of Sail Ships, (16th-18th Century) do any Fishing during their long journey's across bodies of Water?", at https://www.reddit.com/r/AskHistorians/comments/7wzfd7/did_late_age_of_sail_ships_16th18th_century_do/

As well, /u/jschooltiger and /u/expostfacto-saurus replied in "Were naval explorers (Polynesians, Vikings, Spanish) concerned that they would sail forever without hitting land or did they plan to turn back after a certain amount of time? Did they re-supply while sailing (fishing, collecting rain water)?" under https://www.reddit.com/r/AskHistorians/comments/2gfv90/were_naval_explorers_polynesians_vikings_spanish/ckj3mxf/ . Please read it, but I think I can spoiler it: there tends not to be much life where the ocean is deep.

That factor, but also another, are mentioned by QuickSpore in "When Magellan's crew crossed the Pacific and was starving, why didn't they fished the ocean for food?" in https://www.reddit.com/r/AskHistorians/comments/56bobl/when_magellans_crew_crossed_the_pacific_and_was/ .