Abu Dhabi, UAEWednesday 21 August 2019

Sharks at risk for overfishing in the UAE

Scientists study ways of protecting sharks from overfishing.
The blacktip shark is among the largest shark species commonly found in Arabian Gulf waters and grows to two metres or more in length. ARCOF Schneider
The blacktip shark is among the largest shark species commonly found in Arabian Gulf waters and grows to two metres or more in length. ARCOF Schneider

For centuries a staple of traditional Emirati cuisine, the Gulf's sharks remain some of its least-studied creatures.

Little is known about how many species there are, let alone their feeding, ecology and habits.

That kind of data vacuum means that it all but impossible for conservationists to make much more than a guess about how sharks' numbers are changing with time.

A young, Dubai-based researcher is hoping to change that. For more than a year, Rima Jabado has been studying the sharks brought to landing sites along the length of the UAE's Arabian Gulf coast.

So far, Ms Jabado, originally from Lebanon, and a doctoral student at UAE University, has confirmed 26 species in the Arabian Gulf.

She has also interviewed 126 local fishermen about the type of gear they use, their fishing sites and their opinions on whether and how sharks could be protected from overfishing.

The results of the study, which has three more years to run, will be important not only for conservationists but also for the fishing industry, says Dr Aaron Henderson, an assistant professor at the Sultan Qaboos University in Muscat and one of two scientific advisers to the study.

While sharks are a valuable catch for the UAE's fishermen, they are also an essential part of the marine ecosystem. As top predator, their presence keeps many other species, including some that are commercially important, in check.

"The big issue that sharks are facing, is the fact that too many are being taken out," Dr Henderson said. "There is so much fishing going on for them that they just cannot stand it."

For the fisheries to avoid collapse, they need to be regulated, with Gulf-wide rules governing the type of fishing gear allowed, fishing quotas and minimum sizes, to prevent fish being caught before breeding age.

Such rules are common elsewhere - but need to be based on scientific data that takes years to collect.

"For each species, we need to figure out things such as their growth rate, at what age females mature, how many young they produce," says Dr Henderson, who is regional vice chair of the International Union for Conservation of Nature's shark specialist group. "Unfortunately here, in this whole region, we do not have anything like that."

Research such as Ms Jabado's will help, he says. Of the 26 shark species she has catalogued so far, half are smaller - a metre or less in length - and tend to prefer shallower coastal water. Three of these - the milk shark (Rhizoprionodon acutus), sliteye shark (Loxodon macrorhinus), and white cheek shark (Carcharhinus dussumieri) - are used in popular traditional dishes.

The remaining species are larger, growing to two metres or more. They include the blacktip shark (Carcharhinus limbatus), the lemon shark (Negaprion brevirostris) and the spinner shark (Carcharhinus brevipinna), known for its dramatic jumps and spins out of the water as it hunts.

At least one, the great hammerhead (Sphyrna mokarran), is endangered globally. But only two - the bull shark (Carcharhinus leucas) and pig-eye shark (Carcharhinus amboinensis) are considered aggressive. The great hammerhead, an aggressive predator, has been known to attack people, but rarely.

Ms Jabado has recorded all 26 species in the waters around Ras al Khaimah, but has found only 18 off Abu Dhabi, and not the aggressive bull and pig-eye sharks found off Ras al Khaimah.

The eastern emirate is also home to the biggest sharks landed, with fishermen frequently landing hammerheads of three metres and more.

The UAE's waters are also home to whale sharks - the world's largest living fish. These free-roaming ocean species travel vast distances each year, but researchers still have much to learn about their behaviour.

"I am studying all the sharks that I come in contact with at the markets and in the field," Ms Jabado said.

She has even come across a whale shark, although she has also seen evidence of its presence in the form of dried fins on sale at the Dubai fish market.

Whale sharks, though, are the focus of another project, this one by David Robinson, a marine biologist and PhD research student at Heriot-Watt University in Dubai. His SharkWatch Arabia, a database of whale shark sightings founded last August, so far has 57 confirmed sightings. He hopes it will evolve into a tool to help gauge the sharks' abundance in the Arabian Gulf waters.

In April he attached a satellite tag to an eight-metre female whale shark in Qatar. The tag will record the animal's journey for six months - a first for the region - which he hopes will shed new light on its migration patterns.

Ms Jabado, too, is hoping to discover more about migratory patterns but by an altogether different method: experimental fishing.

She has already been out several times in the waters off Dubai and Abu Dhabi, and plans to continue for another year.

To minimise the damage to the sharks, she fishes with circle hooks, rather than the traditional J-shaped hooks. With their sharpest parts pointing, they attach to the shark's mouth rather than its gut.

Once a shark is caught, it is measured and sexed. She also takes tissue samples - tiny pieces of skin from the dorsal fin, less than a centimetre across - to determine the species and genetic relationships, which she will compare with the genetic data of sharks from Oman and Fujairah. After the information is recorded, the fish are released.

Ms Jabado will compare the Arabian Gulf samples against samples from Omani sharks found in Dubai's fish market. She hopes to have genetic data from Dr Henderson and others in time to start her comparison work in October.

She wants to learn whether the sharks migrate between the Arabian Gulf and the Indian Ocean. That, in turn, will assist conservation efforts.

"If a species is migratory, having a management plan in one country only will not work," Dr Henderson said. Instead, consistent rules are needed across all the countries in a shark's range.

Ms Jabado already has some ideas about how the fishery could be better managed. An initial step would be better education for the fishermen.

Sharks breed slowly - and in general, the bigger the species, the slower they breed. Some, such as the great hammerhead, take five years or more to reach sexual maturity. Catching them too young, before they have chance to reproduce, is a sure path to a population crash.

Some, though, breed much faster, making them less prone to overfishing. Milk sharks, for example, are sexually mature at about three years.

These details, though, are a mystery to most fishermen, many of whom struggle even to distinguish between species. A little education could help them to tell the types apart, and know when a shark is too young to be caught.

A closed season would help, too. Unlike most fish, sharks generally do not release thousands of eggs into the water. Instead, the female carries a small number of young for about seven months (albeit without a placenta), before giving birth - usually between February and May.

This spring, Ms Jabado has seen pregnant sharks being landed by fishermen daily. "They are all pregnant," she says. "We are not only losing the mother but any recruitment that can replenish the stock at sea."

 

vtodorova@thenational.ae

Updated: May 15, 2011 04:00 AM

SHARE

SHARE