What is a bull fish?

There is no fish known as a "bull fish." You may be thinking of one of the following:

* Bullhead Shark: This is a common name for a variety of shark species, most notably the Bull Shark (Carcharhinus leucas). They are known for their aggressive nature and the ability to tolerate freshwater.

* Bull Trout: This is a type of trout found in the Pacific Northwest region of North America. It is prized for its fighting ability and its delicious taste.

* Bullseye Fish: This is a colorful, tropical fish with a distinctive bullseye-like marking on its body.

If you could provide more context or a description of what you're looking for, I might be able to help you identify the fish you're interested in.