Fish vs. Fishes: Is it ever correct to say "fishes"?

When Plurals have the same form as their singulars. 

There are nouns whose singular and plural forms are the same, such as “fish,” “moose,” “sheep,” “deer,” and “swine".

These nouns don’t have the normal plural ending because we think of them as a group, as in “We saw deer in the woods.”

The American Heritage Guide to Contemporary Usage and Style uses the example “Half a dozen fishes inhabit the lake” (7).

So you could say:

We caught five fish.

Or:

The commercial troller caught 5000 fish.

We had fish for dinner.

And if you can also say:

There are many fishes in this pond. 

Just remember that the meaning changes. This sentence means that the pond has many species of fish in it. Use "fishes" only for this purpose.