Is it true that a shark is not fish because the has no scales?

That statement is incorrect. Sharks do have scales, but they are not the same type of scales as most bony fish. Here's why:

* Shark Scales: Sharks have dermal denticles, which are tooth-like structures embedded in their skin. They are made of the same material as teeth (dentine and enamel) and provide protection and reduce friction while swimming.

* Bony Fish Scales: Most bony fish have scales that are thin, overlapping plates made of bone. These scales are much smoother than dermal denticles.

So, sharks are definitely fish, just a different type of fish with unique features.