I am unsure if this is intentional, or if its a bug. The only mobs that spawn in the Megalake biomes are the dragonflies. Are fish spawns just not implemented yet? Or is this a bug?

That's all I really have to say, aside from thanking you for porting this mod, it is one of my favorites!

End fish and the jellyfish mobs are in game and working. However t is very possible that sometimes they don't spawn because of the high numbers of endermen and dragonfly around...i will take a look into the spawning conditions

This latest patch seemed to fix this. The fish and jellyfish seem to spawn in megalakes now