The most well known spawning aggregation is that of the mutton snapper. When this aggregation was first fished intensely about 15 years ago, there were reports of commercial longline vessels from the Fort Myers area catching as much as 30,000 pounds of mutton snapper per vessel on a single fishing trip. Today, catch rates are much lower due to the intense fishing pressure Riley's has received. The mutton snapper aggregation still exists, but their numbers have been drastically diminished. If you look a little closer at Riley's Hump, you will see populations of species that exist nowhere else in the continental United States.
Sargassum triggerfish are one example.
Riley's has a considerable population of adult sargassum triggerfish on one small area, perhaps no larger than one acre. How these fish got there, and why they remain only in this one small area, is not yet known. Visibility underwater at Riley's often exceeds 100 feet. Since Riley's is so close to the edge of the continental shelf, and bathed by the Gulf Stream, large pelagic fish often venture over the area. It is one of the few places a diver can look up and occasionally see marlin, sailfish, or dolphin, and look down to see snapper, grouper, and angelfish.