Deformities in sharks could indicate rise in Arabian Gulf pollution

According to Dr Alec Moore, who conducted the study, the abnormalities could also be the result of inbreeding, caused by overfishing.

The blacktip shark, a common sight in the waters of the Arabian Gulf, may be a bellwether for marine scientists as research reveals deformities in the species, suggesting that increased pollution is tShow more

DUBAI // Physical deformities found in sharks common to the waters off Abu Dhabi could be an indicator of increased pollution in the Arabian Gulf, a researcher says.

A survey of 5,958 sharks was carried out between 2008 and 2012 at landing sites and fish markets in the UAE, Bahrain, Qatar and Kuwait.

Of those, 39 blacktips were surveyed in Abu Dhabi, three of which had unusually curved tail fins.

Dr Alec Moore, Indian Ocean vice chairman of the IUCN Shark Specialist Group, said that while abnormalities naturally occur, they also raised questions.

“From examining only a few sharks (39), a relatively high number – three – had abnormally curved tails,” he said

In addition, a further two blacktips – one landed in Abu Dhabi and one in Bahrain – had another type of fin deformity. In all, 10 of the 5,958 sharks examined had abnormalities.

The results, published by Dr Moore in the Journal of Fish Biology, serve as indicators that further research is needed, he said.

More research is necessary before a definite answer is available as to why deformities occur. While some may be the result of injuries, disease or random genetic mutations, it is also “plausible” that pollution from human activities may have a role, too, Dr Moore said.

“Even without humans around, the Gulf is naturally a biologically stressful environment because of high temperature and salinity. It is possible that further increases – from climate change, the daily discharges from desalination plants, and the reduction of freshwater river flow – could be biologically harmful.

“It is also plausible the abnormalities are a result of inbreeding, caused by overfishing,” he said.

In a separate study, the scientist measured concentrations of 11 trace elements in five juvenile and two adult smoothtooth blacktip sharks.

The research was carried out in Kuwait, but the species is also known to occur in the UAE. The scientist found that levels of manganese, lead, iron and mercury in the sharks’ bodies were high in comparison with published records.

Mercury concentrations were among the highest reported in any shark or ray species and exceeded European Food Safety Authority limits. The study is to be published in the Marine Pollution Bulletin.

“It is unlikely that this problem is confined to Kuwait, given the highly industrialised and developed nature of the entire Gulf,” Dr Moore said.

He added that while earlier studies into commercially important fish have not found “pollutant levels to be of major concern to humans”, sharks accumulate more pollutants because they live longer and feed on other fish.

Rima Jabado, an independent researcher into sharks, agreed more needs to be known about local species, for example connecting the presence of deformities with genetic information.

“It is not that I see it every time but I have seen it. It is interesting that it does happen but there needs to be targeted research.”

Obtaining genetic information from sharks with deformities could reveal more about the possible causes. There are many opportunities for research into the area, especially in the Gulf where so little is known about shark populations. A key drawback for researchers is the lack of funding to support such work, Ms Jabado said.