There are phyla or categories of fish?

You're right to use the word "phyla"! While we commonly talk about "types" of fish, the correct biological classification uses phyla for major groupings of animals. However, fish are not a single phylum, but rather a group of animals that belong to several different phyla.

Here's a breakdown:

* Phylum Chordata: This is the phylum that contains all vertebrates, including fish.

* Subphylum Vertebrata: This subphylum is further divided into classes, and fish belong to several of these:

* Class Agnatha: Jawless fish (e.g., lampreys, hagfish)

* Class Chondrichthyes: Cartilaginous fish (e.g., sharks, rays, skates)

* Class Actinopterygii: Ray-finned fish (the most diverse group, including most familiar fish like trout, salmon, bass)

* Class Sarcopterygii: Lobe-finned fish (e.g., lungfish, coelacanths)

So, in summary, fish belong to the phylum Chordata and are spread across several different classes within the subphylum Vertebrata.