What is the meaning of "pelagic"?

[Mr. NiceGuy]

Originally Posted by Mahigeer

My basic understanding is that the;

Bonito, mackerel, yellowtail, sardine, anchovies, tuna are called Pelagic.

They come and go from Baja to US.

I've heard pelagic described this way too, by fishermen, as migrating fish vs. local fish that don't migrate.