The Muskie (or Muskellunge) is a species of fish found in Red Dead Redemption 2.
Compendium[]
Muskies are long, slender-bodied, predatory fish, inhabiting norther lakes. They will ignore food baits and favor lake lures. Muskie are most active on cloudy, overcast days. There are legends of a monster Muskie having been sighted off the coast of Roanoke Ridge.
According to the compendium in game "Using Lake lures will increase your chances of a successful catch".