They can't spawn in the Nether with out using ice blocks so that probably applies to The End as well.
And as for spawning between layers 45 - 62, I don't think that's true. I think they'll spawn wherever there's deep enough water.
okay after hours of testing, made a huge man-made ocean in the End, between layers 62 and 45, no spawning, so im pretty sure they dont spawn in the end, otherwise passive mobs would be running around all over the place
I'm not sure if they do but I know they have to be between layer 45-62. So make sure your on those layers.
And as for spawning between layers 45 - 62, I don't think that's true. I think they'll spawn wherever there's deep enough water.
Try it!
still doesnt spawn =( i even went hundreds of blocks away from the island
Squids wont spawn unless there's water
Then come back and check!
... Well and the Ender Dragon but that can be argued he doesn't spawn in the end but he spawns WITH the end.
http://www.minecraftwiki.net/wiki/Mob_spawning#Mob_Spawning
"The End can spawn only Endermen."