Here are some examples:
* "There are many different fishes in the aquarium." This implies there are various types of fish present.
* "Scientists are studying the different fishes in the lake." This focuses on the diversity of species.
However, when talking about multiple individuals of the same species of fish, you generally use the word "fish".
* "The fisherman caught a lot of fish." This refers to multiple fish of the same type.
* "The children threw fish food into the pond." This refers to a quantity of fish food for the fish present.
In summary:
* "Fishes" is used for multiple species of fish.
* "Fish" is used for multiple individuals of the same species or for fish in general.