Respuesta :

Because fish or deer would only be 1 fishes or deers is more then one .
The term fish is 1 single animal in salt or regular water. The term“fishes” on the other hand, is used to refer or describe the plural of different species of fish (more than one species of fish). and same thing with "deers" AND CAN U MARK ME AS BRAINLIEST ? AND HAVE A GOOD DAY !  :)