Going fishing is actually really helpful in Monster Hunter: World
There's nothing quite like the thrill of the hunt. Monster Hunter: World satisfies the urges of hunters everywhere, silently stalking their prey and then pouncing and battling to completion either alone or with friends.
Another form of hunting, some might say, is fishing. You can do that, too, in Monster Hunter: World, and it's actually quite useful to do so. Certain fish drop very useful consumables, and every fish caught gives you research points as well.
If you find the Piscine Researcher in the Ancient Forest (marked on your map by an exclamation mark), he gives you Critical Bounties, which you can complete and return to the canteen in Astera to unlock new recipes, too.
How to fish
You'll need to be close enough to water that's deep enough to fish in, usually water that's blocked off by an invisible wall. If you can walk in it, you most likely can't fish in it.
A great starting area is the southern shore of the area marked number four in Ancient Forest, where a herd of Kestodon usually converge. Clear them out and head to the water.
In your item bar on the bottom right, scroll until you find the fishing rod, and press Square or X to equip it. You will see a glowing line that signifies where you are aiming your reel, and press R2 or RT to cast it into the water (if it doesn't work, the water isn't deep enough to fish in).
Soon enough, fish will come to bite, and you should be able to see them. If they don't bite right away, wiggle the left analog stick to get their attention. When little fish bite, press O or B and instantly reel them in. If it's a big fish, you'll need to fight with it a little bit by following on-screen button prompts.
Fish and their uses
These fish are incredibly useful, as catching one will drop a scale that can be used in place of your whetstone to sharpen your weapon in the heat of battle. You can hold up to 10 of them.
This fish's scales can be brought back to the canteen and oven roasted to earn you three rations and two herbal medicines.
Although they aren't found until a bit later on in the game, these fish drop scales that can be sold for 1,000 zenny apiece.