It is believed that Greatfish Isle was the home to Zoras before Ganon destroyed it, as Jabun lived there (an obvious altered form of the name Jabu-Jabu from Ocarina of Time) and Zoras are strongly related to water creatures, and the water itself, but it is yet to be decided. Hope this helped :)
I really don't mean to rain on the parade, but the Zoras have already evolved by the events of WW, into the Rito who inhabit Dragon Roost. I think that, since Valoo protects the Rito and the Great Deku Tree protects the Koroks, that Jabun may protect the Hylians. If you look closely at Greatfish Island, you can see what look like the remains of small, wooden houses, hinting at a Hylian settlemented. More support for this is that he moves to Outset Island, another Hylian-established place, which also implies he only lives near smaller villages.