Well my family used to go to Mexico every year since I can remember and there is a place that we would always go swimming it was a river that came out of the mountains the water was crystal clear it could be 10 to 15 ft deep and you could still see the bottom ive always have notice this fish and it only seems to be in this one section of the river I have no idea of what it is ive asked my uncles down their if they now what it is called and they just called it a bluegill or a tilapia I have no pictures and have never found pictures of anything looking like it I havent been their in about 6-7 years now but what I can remember is that it almost had the shape of a bluegill but not as big and as thick as them and they were half black and half white and very aggresive you could feel them bite you as you were swimming buy them just curious if anybody knows what im talking about or have any idea of what they are.