Dab

The dab is a fish. It is in the flatfish group. It has the least letters in its name of all fish, except the ray, which has three aswell. Coincidentally, they are both in the flatfish group. It can be found in the ocean. It, when sold at Tom Nook's store, will get the player 300 Bells.

Further information
The common dab is the smallest flatfish in the world. It can be found on sandy seabeds, most commonly in the North Sea off the east coast of England.