Tang is eaten all over the Pacific Rim and Asian countries. I personally would love to have one of those fish in my tank, but I can't say I am outraged at a picture of them being ready to be sold/cooked.
There are many beautiful creatures on this planet that we eat, if you really have a problem with this, become a vegetarian, I on the other hand will continue to be an omnivore.
And while I do believe that over fishing can be a problem, I don't believe it is a problem in this instance since these photos are from Hawaii.