An ‘Alien-like’ parasite that eats the tongues of fish and then occupies their mouths is more prevalent in areas suffering from ‘predatory’ overfishing, according to research from the University of Salford.


Dr Stefano Mariani and colleagues from University College Dublin and the University of East Anglia made the discovery as they inspected stocks of striped sea bream in the Mediterranean Sea, and determined that the fish caught near a Spanish area protected from fishing were much less affected by the infection Ceratothoa italica than specimens from heavily fished areas in Italy.


Almost half (47 per cent) of the fish from the non-protected area were found to be infected with the parasite, compared with 30 per cent from waters close to areas where fishing is banned.


In addition, the researchers noted that while the parasite infection significantly hampered growth and condition in the Italian fish, it had no discernible impacts on the physiology of the Spanish fish, writes FIS.COM.


Named ‘Betty’ by the team’s PhD graduate Maria Sala-Bozano, Ceratothoa italica spawns by swimming between fish as a juvenile and entering the mouth after penetrating the body through the gills. A female parasite will then take up position on the tongue, virtually replacing it, and feeding on blood as it matures to adulthood.


The parasite does not pose any risk to humans, but it does reduce size and life-expectancy of the fish.


The researchers were careful to establish that the fish in the two Mediterranean areas were living in very similar environmental conditions and the populations of both fish and parasites were genetically very closely related.


As the Spanish area was better protected from overfishing than the Italian, the report suggests this is a major factor in the spread of virulence of the parasite.


“This is further evidence that human over-exploitation of fish stocks has adverse and far-reaching effects,” Mariani from the School of Environment & Life Sciences said. “Areas with poor regulation have smaller, younger fish and, as we’ve now demonstrated, higher and more harmful parasite infestations.”


“Betty is quite gruesome and does remind you of the Alien films, but it’s a highly adapted and specialised animal which is very successful. Unfortunately, over-fishing upsets the balance of parasite and host and interferes with the whole eco-system,” he continued.


He asserted that establishing protected areas makes sense in order to safeguard both the quantity and the quality of the fish many people rely on for sustenance.