Bass'ken Lake's Rare Fish
Bass'ken lake has 3 different rare fish to be caught. Mutha Guppa, Big Mouth Bass'terd and Candy Striper. They are available at different times during the game; Day, Night and Dusk/Dawn.
Many people wonder if you will be able to tell when you have hooked a Rare Fish. My answer is "Yes". Their movement isn't similar to any other fish in the lake. In the case of Bass'ken, these fish will move fast; faster than stripers; which means that if you are used to fishing in the lake, you will feel the difference almost immediately. Keep in mind that all rares in a lake move in the same way.
Now, lets move onto the fish:
Mutha Guppa:

This rare fish can be caught during Day time. The catch description will say: "Dang gurl! Baby got back!"
You can trade 10 of these fish for a Mutha Guppa Mask or for a Mutha Guppa Armored Arm if you have a Gold Automaton Arm in your inventory.
Big Mouth Bass'terd:

This rare fish can be caught during Night Time. The catch description will say: "OMG! HE'S HUGE!"
You can trade 10 of these fish for a Big Mouth Bassterd Mask or just 5 and a Bullet Belt for a Big Mouth Bassterd Belt
Candy Striper:

This rare fish can be caught during Dawn or Dusk. The catch description will say: "I don't know why anyone would volunteer to be caught."
You can trade 10 of these fish for a Candy Striper Helmet or 10 and a Royal Red Crown for a Candy Striper Candy Crown.