I’m guessing that the oil platforms have more fish due to the greater range in depth around the structure. A natural reef probably has a limited depth range, and only attracts fish that like those depths.
Either that, or it is a diabolical scheme between the oil and fishing industries to gather all sorts of fish in one area and then catch them all - and then served to yuppies (is that still a thing?) at fancy New Orleans restaurants.
BTW - if salmon is on the endangered species list - how come it is still on the menu?
Wild salmon vs. farmed salmon.