MOHAMED KHOULAIDI

DOHA THE unusually large aggregation of whale sharks in the Al Shaheen area within Qatari waters could well be the largest in the world, a ministry of environment expert said on Wednesday.

“Frequent observations by workers on offshore platforms, supplemented by research activities by the Ministry of Environment, have contributed to the understanding that an unusually high number of whale sharks aggregate in Qatari waters, particularly in and around the Al Shaheen Field”, Mohammed al Jaidah, Environmental Expert at the Ministry of Environment told a press conference.

Whale sharks are the largest fish in the sea, measuring up to 20 metres in length and can weigh more than 30 tonnes. But very little is known about the whale shark population that visits the waters of Qatar each summer between May and September.

It is believed that one contributing reason for the sharks’ presence in the Al Shaheen oil field may be the large offshore platforms. The structures form an artificial reef environment for fish, and fishing restrictions ensure large fish stocks prevail. The spawning fish provide a food source for the whale sharks, attracting them in large numbers to the area in the period from May to September.

In order to study the phenomenon, a team of Qatari and international researchers, accompanied by a world-class underwater camera team, undertook a 12- day research expedition last month. The expedition was conducted under the Ministry of Environemnt’s (MoE) Qatar Whale Shark Research Project with Maersk Oil Research & Technology Centre (MO-RTC) support.

The team encountered around 200 whale sharks during the trip, identified 107 and found among them, 13 had they had encountered during surveys last year. The researchers also took samples of fish spawn, thought to be the whale sharks’ primary food source, for tests to assess relationships to other whale shark populations and feeding patterns.

While initially the programme focus is on whale shark (Rhincodon typus), it will eventually explore and document the diversity and abundance of marine species in Qatari waters, particularly those found in the vicinity of the Al Shaheen field. The MoE signed a Memorandum of Understanding (MoU) with MO-RTC in this regard in March.

During the recent expedition the team performed a number of scientific research activities and even made some scientific breakthroughs, Mohammed said.

“This work was captured on film, and a documentary will be made for use in Qatar to broaden awareness and understanding of this unique population and the research work that is ongoing.

“We deployed 10 acoustic transmitters on individual whale sharks (40 more are expected to be deployed this year) and 15 acoustic receivers that can detect whale sharks that have acoustic transmitters attached to them” explainedSteffen Bach, environmental theme lead at the MO-RTC who was on the expedition team.

“In addition, seven satellite tags were attached to individual sharks in order to track movements within the Gulf and beyond and we performed photo ID and spot pattern identification” says Steffen. “We encountered around 200 whale sharks during the trip, of which 107 were identified - 13 of whom we had encountered during surveys last year”.

Whale sharks grow to enormous sizes. Fish length is important for many reasons; at smaller sizes sharks have more risk from predation, whereas larger individuals may have the capacity to produce more offspring.

This fact can pose some practical difficulties as it is very difficult to accurately measure a bussized fish while it is swimming underwater and scientists have put some considerable effort into solving this problem.

Various ideas have been tried, such as comparing the shark’s length to a nearby swimmer, or even swimming alongside the shark with a measuring tape.

A new, and rather easier strategy, involves a digital camera and parallel- mounted lasers. Every whale shark has a distinctive pattern of spots that allows scientists to identify individuals from photographs. The scientists have fitted their camera onto the centre of a steel frame, from which each end has a mounted green laser pointer.

The laser dots are calibrated to be 50 centimetres apart on the side of the shark, so in one photo they can ascertain both the identity of the shark and have a precise scale bar for accurate length estimation.