Far Cry New Dawn has 6 Fish Locations. Catching every type of Fish unlocks the You're a Catch trophy or achievement. To do this you must first buy the perk "Fishing Rod". This adds a fishing rod to your weapon wheel. The "Outdoor Enthusiast" perk is also recommended because it makes catching fish easier.

All of these are available from the beginning of Act 1, but can still be done after the story in free-roam.

Select the Fishing Rod from the weapon wheel and put it in the water at the Fishing Spot. Then press L2 (PS4) / LT (XB1) for a split second to make the lure wobble in the water just a bit. Don't press too long as it would reel in the lure, which you don't want. Only press for a short moment to attract the fish with the lure. Keep pressing L2 / LT in quick succession until you get a bite. Then hook the Fish by pressing R2 / RT and reel it in. When the fish swims to the side, put the left stick in the opposite direction (so when the fish swims right you push left, when it swims left you push right). Do this until you've reeled it in. Go for the low difficulty fishing spots as they are easier to reel in. You only need to catch the fish once with any rarity level to count for the "You're a Catch" trophy. You do not have to catch it in all rarities.

You also gain 1 Perk Point for each fish!