Oh, but fish do enjoy a good play on words! Or, a play on words, at any rate.
And this particular play on words is just about irresistible to fish! (We've seen it before here and here.)
They're all about the hook, those fish. And why shouldn't they be? The hook represents their highest aspiration: to be jerked from the nurturing waters and dragged into the deathly air, where they may succumb in paroxysms of pain.
Do you see? While the fish in the foreground is cracking wise (or, you know, "wise"), the fella in back has a notion to bite down on that hook. He knows it's a trap—the Head Fish's line is hardly subtle—but he wants it all the same. Fish get a bad rap. We're told that they have the feeblest memories (not true). That they are impelled by nothing more than overpowering instinct. Now we plainly see that fish aren't stupid. It is just their all-encompassing wish to die that makes them seem that way to us.
And however you interpret the fish's exhortation to "get hooked"—is he encouraging other fish to join his cult or more fishermen to start killing fish?—it's a warped worldview only a twisted fish could espouse.