A drop in fish population in the Mediterranean has been attributed to the rise of jellyfish in the region, according to a new report by the U.N. Food and Agriculture Organization.

The report said that overfishing in the Mediterranean and Black Sea has removed the top predators, and so has let the jellyfish numbers soar.

Moreover, medusae feed on fish larvae, which "further reduce the resilience of fish populations already impacted by overfishing," the report added.

Mnemiopsis leidyi, a jellyfish species that live in the Atlantic, were accidently introduced in the Black Sea in the early 1980s, which led to an unprecedented boom in their numbers. The severe effect of the jellyfish surge brought down the numbers of fish in the region.

The population of this jellyfish was reduced with the arrival of Beroe ovate, the natural predator of the Mnemiopsis leidyi.

However, the presence of the Pelagia noctiluca jellyfish - which has a vicious sting - along with impacts of overfishing has reduced the fish population.

"In the past, the system could cope with episodes of jellyfish abundance, but in the case of the early 1980s blooms, the system went in another direction and is still not back to "normal" in pre-Pelagiayears," the report said.

A recent study too had found that overfishing has led to a surge in the population of the jellyfish not just in the Black sea, but across the world. Another study that was published last year had said that the jellyfish population was increasing in 82 percent of the regions analyzed, which included East Asia, the Black Sea, the Mediterranean, the Northeast U.S. Shelf, Hawaii, and Antarctica. The invasion of these creatures is destroying fisheries in many regions.

Global warming, which helps tropical species thrive, and increase in nutrients in the ocean, along with safe places for the jellyfish to go through the polyps stage are among reasons for the increase in jellyfish population, FAO said.

The report, "Review of Jellyfish Blooms in the Mediterranean and Black Sea", can be read here.