This is a Spotted Eagle Ray - a big, glorious creature that is classed on the IUCN Red List as Near Threatened. This means there aren't as many of them as there should be, due to human activity. They're not especially tasty, but get eaten in certain areas of the world where most things are considered food, tasty or not. There isn't really much you can do about this directly, unless you are a Southeast Asian fisherman - in which case, don't take these guys to market. Let them go. But if you see such things on a menu on your travels, don't order them and say something. One person saying something once may not make a bit of difference, but a significant proportion of the tourist industry, making responsible purchase decisions and being vocal about it? That will change things. And it will help these communities in other ways too - large pelagics such as Eagle Rays are worth a lot more to local economies alive than dead.