So…Splatoon Raider has flying Salmonids that somehow turned fins into wings to fly like birds. I’ll note that said fins don’t connect to the body beyond where the joints are. It is literally oversized fins they can flap to use as wings with otherwise fish-shaped bodies.
Ignoring how this is Splatoon and how the Salmonids aren’t normal fish (especially since the ones in Raiders might be powers up by getting high on effectively magic salt), would this be a realistic things to have happen eventually? Or is it something straight out of fantasy with how fins compare to arms and wings?
considering we already have multiple species of flying fish in real life, some of which can glide for pretty dang impressive distances, and considering that insect wings similarly only have a single joint connecting the base of the wing to the body, I do think there's space for speculative evolution about fish with insect-like wings that can fly for real instead of just gliding.
(image description: photo of a ladybug spreading its wings. photo of a flying fish with four large fins spread as it glides. photo of a dragonfly in flight. end description)
you can see here that the shape of a flying fish's wings are not all that different from the shape of insect wings! they just need enough strength to flap and maybe a modification to breathe air as well (there are also real fish like that) and you've got a fish that can perform powered flight! not too far outside the realm of possibility in a fantastical setting or a far-flung future earth.
