Fish and dolphins spawn in water above sea level

Fish mobs and dolphins seem to be able to spawn in water blocks way above sea level in their corresponding biomes. I noticed it in a survival world, where a Dolphin dropped onto land from a flooded mob spawning platform in the sky. Also tested in Creative mode above a lukewarm ocean and saw cod, pufferfish and tropical fish spawning.

This seems inconsistent with squid spawning, which is limited to certain Y levels.