The National/UAE-Daniel Bardsley,
3/11/17
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.
Posts
