The mesh file I think is a part of a mesh pack which I will link below~ But yes, I do think you can turn it into an item, once you rig the item to the character to move with them and things like that. It is sometimes easier talking to someone like Ruby, shes good with that kind of stuff ^^ But, turning it into an item will not mess up your game.
>>Click me for Fish Mesh Pack<< (http://www.deviantart.com/art/F-i-s-h-P-a-c-k-383322637)
~ Whisper