Fish are food items that you can gather on the map so it would make sense for them to be foraged items. However, for the purposes of this battle royale game, they are not. It is worth keeping in mind that fish in Fortnite is in their own completely separate category of items. Sure, they will largely do a lot of the same things as the foraged items do. There are different types of fish, some granting health upon consumption while others grant shields and so on. That said, they do not fall under the category of foraged items since there are some key differences. For one, fish in the game can be added to your inventory for later whereas most foraged items cannot. Furthermore, foraged items simply require interaction to consume or get them and that is it. On the other hand, fish require you to find a fishing rod or other tool beforehand and then patiently fish for it. Most importantly, though, there is a practical reason for why you should know the difference between fish and foraged items. There are challenges that pop up occasionally in Fortnite that will task you with finding several foraged items. If you try to get fish, you will find that these items do not count towards the total for that mission. Foraging items have their own unique challenges that Epic Games releases for them occasionally.