IF YOU’RE one of the dozens of people who enjoys anchovies on your pizza, we have bad news for you: the world may soon be facing a shortage of the salty little fishes.

This year, a massive swarm of invasive jellyfish called Mnemiopsis leidyi has invaded the Adriatic Sea off the coat of Italy, wreaking havoc with the anchovy spawning season, New Scientist reports.

The comb jelly, which has no natural predators, spreads at an alarming rate, feeding on zooplankton, the food of many commercially important fish including the anchovy.

The comb jelly devastated fish stocks in the Black Sea after arriving via the ballast waters in oil tankers from the American Atlantic in 1982, costing the seafood industry billions of euros by the mid-1990s.

While it has been observed in the Adriatic since 2005, this year the problem is much worse. New Scientist reports huge swarms have been spotted along the coast of northern Croatia, and the coasts of Slovenia and Italy, with jellies filling lagoons in northern Italy since July.

“This is the first time that this species has existed in such masses in the Adriatic,” Valentina Tirelli from Italy’s National Institute of Oceanography and Geophysics told New Scientist.

Davor Lučić from Croatia’s Institute for Marine and Coastal Research told the magazine that certain points, population densities were estimated to be up to 500 specimens per square metre.

“Estimates were made for the adults only, but we assume that there were significantly higher numbers of juveniles,” he said.

According to a 2012 report by the UN Food and Agriculture Organisation, Australia is Italy’s second-largest export destination for anchovies. In 2010, Italy exported 3700 tonnes of anchovies, 10 per cent of which came to Australia.