South African city Gansbaai has been known to be one the the worlds locations with the highest clustering of white shark populations. This region alone used to have about 2,000 great white sharks but it has been recently found that that number could actually be far below what it should be. The Dyer Island Conservation Trust finds that the great white population is actually lower than that meaning that they should now be classified as a threatened specie.
They way that they came about these numbers was by cataloging the dorsal fin of each white shark. Interestingly, each shark has a unique dorsal fin. Examples of the uniqueness can be described as wolfgang (pointed top with ridges), notch, and slash fin (which looks like chunks are missing from the fin). Through the collaboration of the Dyer Island Conservation Trust and the Marine Shark Cage Diving company, marine biologists were able to shoot aver 20,000 pictures of great white fins. They then compiled all of the pictures and were able to identify 532 sharks.
With an algorithm they found that there are only a maximum 1,000 inhabiting the waters pif Gansbaai. With numbers like these, the initiatives to help preserve this amazing species are closely monitored and advocated for. [via]