Sea snakes of the Gulf are focus of new research

Two years of research has discovered that there are in fact 10 species of sea snake in the Gulf, one more than previously believed, but there still remains a lot to learn about these elusive creatures.

Sea snakes are not a major danger to people as they tend not to attack unless provoked. Even when they bite, venom is rarely released. Courtesy Mohsen Rezaie-Atagholipour
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For many UAE residents, the only time they hear about sea snakes is when occasional warnings are made to beachgoers to steer clear of the creatures if they are found on the sand.

Although they are sometimes found washed up on beaches – they have difficulty moving on land, so can appear to be dead when they are alive – and are occasionally spotted in the water, sightings are not common for most of us.

Similarly, sea snakes in the Gulf have tended not to attract the attention of scientists.

Much of what is known about them is locally based on research from the first half of the 20th century. Such studies indicated that there were nine species of the subfamily Hydrophiinae, which includes sea snakes, in Gulf waters.

But researchers have now comprehensively updated their knowledge of local sea snakes by carrying out a detailed survey of their distribution in Gulf waters, work that has been published in the journal ZooKeys.

The study mostly looked at sea snakes found in fishing nets in Iranian waters as “bycatch”, meaning they were not the vessels’ target species.

One of the researchers carrying out the fieldwork, and the senior author of the recent paper, was Mohsen Rezaie-Atagholipour, of the environmental management office of Qeshm Free Area Organisation.

During 2013 and 2014 he and his colleagues spent time on trawlers at several locations in Iranian waters, including in the Gulf of Oman, collecting sea snakes that had been caught in the nets. Fieldwork was also carried out in mangrove swamps.

In the two years that followed, the scientists, helped by a French-based researcher, Dr Nicolas Vidal, carried out a detailed analysis of the specimens to identify which species they came from.

They found that there were 10 species present from the Hydrophiinae family, which includes sea snakes. One of them, Microcephalophis cantoris, which was found in the Gulf of Oman, had not been definitively recorded in the area by scientists.

Until this study, the nearest confirmed findings of M cantoris had been made off Pakistan.

“It’s the first time it’s been found in this area and its range is extended for more than 400km,” says Dr Vidal.

This species is, says Mr Rezaie-Atagholipour, very rare in the area, which could account for no previous scientific study having definitively identified it in the region.

“We reviewed all assessable literature but, except our record, there is no historical confirmed record of the species in both gulfs,” says Mr Rezaie-Atagholipour.

“It, however, seems likely that the species is not abundant even in other parts of its geographical distribution range as we have few information about this species.”

As the scientists note in their paper, sea snakes of the Hydrophiinae family have a common ancestor dating back about 6 million years, although it is in the last 3.5 million years that most of the types that now exist evolved.

There are more than 60 species of hydrophiines in total, with the creatures being found off the east coast of Africa, off South Asia and around Australia and many other parts of Asia-Pacific. They evolved from Australia’s highly venomous land snakes, which helps to explain why they are venomous.

Typically growing 120 to 150 centimetres long, sea snakes have much reduced scales on their underside, meaning they are largely helpless on land. They have shorter tongues than land snakes, because detecting scents is easier in the water than on land. They have valves over their nostrils to keep out water and, as well as breathing through these nostrils, they can also exchange gases through their skin.

Catching prey is largely done through detecting vibrations or sounds and through smell; vision is less important.

They mostly eat fish and other sea life, such as crustaceans. Fortunately, they are not a major danger to people as they tend not to attack unless provoked and even when they do bite people, in most cases no venom is released.

The fact that sea snakes are often found in nets as bycatch raises the question of whether human activity is affecting their numbers. All species found locally, except M cantoris, are classified as "least concern" by the International Union for the Conservation of Nature.

But there could still be issues over abundance locally, says Mr Rezaie-Atagholipour, because the union classification is based on the species’ abundance across its geographical range.

It does not mean that numbers in a specific habitat, such as the Gulf, are not falling.

He indicated that bycatch is probably the greatest anthropogenic threat to sea snakes in the area.

“Some people may think that fishing nets are not a threat for sea snakes because the body diameter of these tube-like creatures is smaller than the mesh size of most fishing nets. This is absolutely wrong,” Mr Rezaie-Atagholipour says.

“Sea snakes can easily become entangled in fishing nets due to their long body. Most sea snakes I’ve collected from fishing nets were dead or badly injured, mostly because of pressure by other bycatch or drowning.”

Sea snakes found locally are noteworthy, Mr Rezaie-Atagholipour says, because they had adapted to live in the harsh Gulf environment, where temperatures are high, there is little rainfall and the water is highly saline.

“Therefore, sea snake populations in the Gulf are important if we want to know what will be the effects of climate change and global warming on these highly venomous marine reptiles,” he says.

“Nonetheless, our information about the biology and conservation status of sea snakes living in the Gulf is scarce. Unlike the Western Indo-Pacific region, known as a biodiversity hotspot for sea snakes, they are not diverse nor abundant in the Gulf.

“I always ask myself, do we have enough information about sea snakes living in the Gulf to know if we are losing them in our area? I feel disappointed when I see the answer is still ‘no’.”

A little more should be known about sea snakes locally when the scientists publish a further study that will look in more detail at the morphology (structure and appearance) and the genetics of the creatures. Fascinating but not well studied, the Gulf’s sea snakes should be yielding up a few more secrets in the years to come.