several causes provoked a dramatic population decrease over time: on one hand, commercial hunting (especially during the roman empire and middle ages) and during the 20th century, eradication by fishermen, who used to consider it a pest due to the damage the seal causes to fishing nets when it preys on fish caught in them; and on the other hand, coastal urbanization and pollution. currently, its entire population is estimated to be less than 600 individuals scattered throughout a wide distribution range, which qualifies this species as endangered. its current very sparse population is one more serious threat to the species, as it only has two key sites that can be deemed viable. one is the aegean sea (250–300 animals in greece, with the largest concentration of animals on gyaros, and some 100 in turkey); the other important subpopulation is the western saharan portion of cabo blanco (around 200 individuals which may support the small, but growing, nucleus in the desertas islands – roughly 20 individuals). some individuals may be using coastal areas along other parts of western sahara, such as in cintra bay. these two key sites are virtually in the extreme opposites of the species' distribution range, which makes natural population interchange between them impossible. all the other remaining subpopulations are composed of less than 50 mature individuals, many of them being only loose groups of extremely reduced size – often less than five individuals. consequently, low genetic variability exists.