Calls have been made for marine protected areas in Abu Dhabi waters to be made larger to protect a dolphin species facing threats from human disturbance and climate change.
Scientists made the appeal after they found that local numbers of the Indo-Pacific bottlenose dolphin may be declining.
Observations during scores of boat trips by researchers also showed that the species preferred waters off western and central Abu Dhabi emirate, where there is less human activity that could affect the abundance of prey.
The work by the Spanish-based Bottlenose Dolphin Research Institute and the Environment Agency Abu Dhabi is being published in the journal Marine Biology.
“The destruction of habitat, it’s possible it’s one of the biggest impacts. If we have protected areas, we’re saving the habitats,” said Dr Bruno Díaz López, first author of the study and the BDRI’s chief biologist and director.
“It keeps it pristine. It will keep the food for the dolphins and many other species... It’s a priority.
"In the western region there should be new protected areas or we should make larger those that exist,” he added.
While marine protected areas cover 13.45 per cent of Abu Dhabi’s waters, the researchers say that coastal areas are being disturbed by port construction, boat traffic, fishing, oil and gas activity and land reclamation.
Are UAE dolphin populations declining?
Using a 45-foot boat, they sailed out into the Gulf on 80 days between June 2014 and November 2019, and spent more than 500 hours looking for the creatures.
The dolphins were typically in pods of eight or nine, although there could be as many as 45 in a group. To identify individuals, photos were taken of both sides of the dorsal or upper fin, which has markings.
They found more than three times as many individuals, 130, in the central region of Abu Dhabi waters than in the eastern region, despite spending similar periods of time, about 190 hours, in each.
Differences in marine traffic, habitat degradation and pollution are thought to account for the differences. In the western region 286 dolphins were seen during 150 hours of observations.
Less disturbed areas may be preferred because they contain more prey, which for the Indo-Pacific bottlenose dolphin includes various types of fish, as well as squid.
Based on their observations, the researchers estimated the total population of the species in Abu Dhabi waters was about 782 individuals.
“Our findings support the call for increased marine protected areas and the creation of transboundary conservation areas in the region,” the researchers wrote in their paper.
“Regional connectivity should be of value to marine predators whose wide distribution and vulnerability to human activities means that alteration of their habitats can result in population declines and eventual local or regional extinctions.”
There are examples where countries have worked together to create transnational conservation areas, said Dr Díaz López, including in the Mediterranean and in American waters.
Some individuals were spotted on separate days in locations hundreds of kilometres apart, with the animals moving long distances in search of food.
Numbers fell during the five-year period when observations were made, although Dr Díaz López said it was important “to be careful” before concluding the species was declining locally.
“To detect a trend we maybe need more than 10 years of data to be sure it’s not a particular year,” he said.
The effect of climate change on UAE waters
The Indo-Pacific bottlenose dolphin or Tursiops aduncus is one of three bottlenose dolphin species and can be found in an area stretching from Africa’s south-east coast to the Solomon Islands, east of Papua New Guinea.
Described as “near threatened” globally by the International Union for Conservation of Nature, it can be affected, say the researchers, by overfishing, habitat damage, pollution, noise, boat strikes and accidental “by-catch” from fishing.
The species is particularly vulnerable because it is large, grows slowly, matures late, gives birth to just one calf at a time and has a long interval between births.
Other mammals found in the Arabian Gulf include the Indian Ocean humpback dolphin, the finless porpoise and the dugong.
Because climate change is likely to make conditions more difficult for the species in what is already one of the world’s most extreme marine environments, Dr Díaz López said it was important to limit other sources of harm.
“We can minimise the other problems, the human problems,” he said. “Otherwise, it’s true, climate change... is impacting the Gulf. It’s been seen in the bleaching episodes of corals.
“We need to be extremely careful, it’s like a domino effect. If one piece falls, maybe everything is going to fall.”
Before the fieldwork began, in 2013 EAD researchers travelled to the BDRI’s headquarters, which were in Italy at the time, to receive training.
In emailed comments, Dr Himansu Das and Maitha Al Hameli, respectively EAD’s unit head and lead specialist for marine threatened species and habitats, said dolphins and other marine mammals have large home ranges and move between the countries with coastlines on the Gulf.
“Therefore, trans-frontier conservation areas can be useful,” they said.
“However, the possibility of having these depends on various factors beyond the control of researchers. Hence, until that time, local conservation actions within our geographical boundary must continue.”
They said a key aim of the latest study was to help develop a conservation action plan for cetaceans.
During the same boat trips, observations were made of other species, including the finless porpoise and the dugong, and the researchers hope to publish findings on them as well.
In 2014 and 2015 BDRI and EAD researchers assessed the abundance of the Indian Ocean humpback dolphin, and published their findings three years ago. They estimated there were about 701 individuals of that species in Abu Dhabi waters.
This new study - titled 'Vulnerability of a Top Marine Predator in One of the World’s Most Impacted Marine Environments (Arabian Gulf)' has been released online in preliminary form before being reviewed by other researchers.
