Shark population in Gulf waters higher than thought

A survey of the Gulf's shark population has revealed the presence of at least 29 species, rather than the dozen or so previously identified.

Rima Jabado takes DNA samples from sharks at the Abu Dhabi Fish Market in January this year.

The good news for anyone still haunted by the theme music to the film Jaws every time they step into the sea is that there are almost certainly no great white sharks cruising in the Arabian Gulf waters off the UAE.

Nor, according to the results from a unique year-long survey of the Gulf's shark population, is one likely to run into the equally notorious mako or oceanic whitetip - the species blamed for attacking five tourists, one fatally, in shallow water off the Red Sea resort of Sharm El Sheikh last December.

The even better news, from an ecological viewpoint, is that there are no fewer than 29 species of sharks out there, ranging in length from the white cheek - at 36 centimetres the smallest found - to the frankly intimidating great hammerhead, the largest example of which caught off the UAE was 3.82 metres long.

Oh, and there is a slim chance that swimmers could encounter the notoriously tetchy tiger, sandbar, grey reef and bull sharks, and even the creature most feared by generations of pearl divers - the sawfish, a monstrous member of the ray family, aka the carpenter shark. It is listed as critically endangered by the International Union for Conservation of Nature and Natural Resources (IUCN) but is nevertheless clinging on to life in the Gulf.

Just over a year ago Rima Jabado, a Lebanese-born Canadian doctorate student at UAE University in Al Ain, embarked on the first scientific survey of the shark population of the Gulf, a scientific cul-de-sac that until then had been strangely ignored, despite worldwide concern about declining shark populations.

Popular wisdom, gleaned from fishermen, had it that there were probably about a dozen different species of shark out there - a number Ms Jabado found to be a wild underestimation within a few months of starting work.

The lack of knowledge, however, at least made designing her study a breeze.

"It was very easy," she says, laughing. "I needed to know everything; there was just no information."

But how to go about counting creatures few people ever see? Ms Jabado's ingenious if labour-intensive solution lay in the catches of the UAE's commercial fishermen. Since last October she and a team of volunteers have made more than 140 visits to the fish markets of the UAE, twice a month each to Abu Dhabi, Sharjah and Ras Al Khaimah and four times a month to Dubai.

In the process she has seen, identified, photographed and measured 14,627 individual sharks - among them 67 of the largest species of hammerhead (Sphyrna mokarran), capable of growing up to six metres in length and listed as endangered by the IUCN. More than half of these were caught by fishermen from Abu Dhabi.

Without a previously established baseline with which Ms Jabado can compare her results, she has no idea yet if the shark population is thriving or failing, but says she has been pleasantly surprised by the numbers she has seen "in these extreme environmental conditions".

"I didn't expect this amount of sharks, or species, in the Arabian Gulf," she says.

"Everyone says it is low on biodiversity because the conditions don't allow a lot of species to survive, but the diversity of sharks and rays I have found is comparable to the Red Sea, which is one of the seas with the highest biodiversity." Her key finding is that although there are at least 29 species present in the Gulf, just six types of shark account for just over 91 per cent of the total population.

At 33.59 and 31.73 per cent, the spottail (Carcharhinus sorrah) and the milk shark Rhizoprionodon acutus), which grow to a maximum of about 150cm and 100cm respectively, are by far the most numerous. Next is the common black tip (Carcharhinus limbatus, 11.06 pere cent of the total), which can grow to 250 centimetres and is regarded as "near threatened" (and potentially threatening: according to the Shark Trust it "should be treated with respect when stimulated by food"), followed by the Slit-eye (Loxodon macrorhinus, 8.19 per cent), the whitecheek (Carcharhinus dussumieri, 5.03 per cent and also threatened) and the Smooth-hound (Mustelus mosis, 1.41 per cent). None of these last three exceeds 150 centimetres in length.

Each one of the other 23 identified species accounts for less than 1% of the total population - and some are very rare indeed, including three Sandbar sharks (Carcharhinus plumbeous) landed in Ras Al Khaimah; the solitary tiger (Galeocerdo Cuvier) and Sawfish (Pristis zijsron), both from Sharjah, where the only two Grey reef sharks (Carcharhinus amblyrhynchos) were also landed.

Thanks to the DNA samples Ms Jabado has harvested from more than 8,000 sharks, that tally of 29 species could grow even larger.

"Morphologically similar sharks can be two completely different species and this is something we are finding out only because of genetics," says Ms Jabado. Often, species can be told apart only by a single, obscure visual clue, "something missing morphologically, perhaps, and sometimes difficult to detect by eye in the field; or you might need fine measurements to determine, say, that the ratio between the first and second dorsal fin is less than 3:1, showing it is really a different species".

Ms Jabado now faces months of work in the lab, sequencing and analysing the 8,000 DNA samples. When the results are in they will be added to the online Fish Barcode of Life Initiative, a database run by the Canadian Centre for DNA Barcoding at the University of Guelph - and she is cautiously hopeful that some surprises will surface.

"There are a few sharks I haven't been able to identify, so maybe we have found a new species or two. I can't say definitely but hopefully the DNA work will be able to confirm that."

Some, however, such as the sawfish, are in danger of disappearing. "All the fishermen I talked to said 'Oh, it was all over the place, we used to use the saw for barbed wire for our houses', but now it's become so rare, not only here but across the world."

With 14 months of hands-on research, Ms Jabado now has data for two consecutive years from the months of October and November - and intends to press on at least for another year. What she has created already is a vital baseline for future research. A similar study carried out a decade from now, for instance, would expose any significant changes in species numbers. But if she can get funding, she would like to continue sampling fish catches for another two years, "so I can start looking at trends and migratory patterns".

Why, for instance, did three particular species of shark landed in abundance during August, September and October suddenly disappear from catches? One theory is that these are migratory species, or sharks that come to the area only to breed, but only year-on-year data can confirm this, and indicate whether or not they should be protected at certain times.

Ms Jabado also hopes her work will help the UAE to fulfil its commitment to the International Plan of Action for Sharks, adopted by the UN Food and Agriculture Organisation (FAO). Under the scheme, all countries where fishermen catch commercial quantities of sharks were obliged to develop a National Shark Plan by 2001, but barely 10 per cent have. "Progress in most states," says the FAO, "remains disappointing".

Ms Jabado says: "The UAE was a signatory to this code of conduct but 12 years down the line there is still no national plan of action for sharks in the UAE or in any other country in the region, for that matter. There are different types of data that need to be collected to be able to put together a national plan.

"You need to assess shark stocks in a country by addressing what species are there, what are the main threats that they're facing and look at numbers and abundance. None of this information has been available for the UAE."