Primetime Angler is a gear perk that makes hooked fish tire out faster in daytime. Fishing in Far Cry 6 feeds money and Fishing Hut upgrades, so this shortens the reel fight when you farm during the day.
Once a fish is on the line, its stamina drains faster during the day. You land it sooner and risk the line less.
Wear the Gar Baseball Tee in the chest slot. Gear perks are fixed to the piece of clothing that carries them, so you get this one by wearing that piece, not by unlocking it in a menu.
Still Waters stops predators attacking you while you fish, and Improved Reel Speed makes each pull count. Swap the set on only for fishing sessions.