[ELI5] why do some fish like Snapper have scales but other fish like Tuna do not?

Question

[ELI5] why do some fish like Snapper have scales but other fish like Tuna do not?

In: Biology

Answer 1

Tuna are built for speed and power, just ask any game fisherman, and they have smoother skin to allow for this. Snapper, on the other hand, are a lot tougher and more likely to fight, meaning they need the scales to protect themselves.

You may notice that, typically, larger fish, sharks, tuna, etc, tend to have smoother skin, while smaller fish, brim, carp, snapper, etc, tend to have rougher skin. The same applies for different body shapes. Whiting have smoother skin and narrower bodies, for instance