November 4, 2009 - DON’T be surprised if you end up face to face
with sharks while diving in the waters off Singapore.
Yesterday, The New Paper reported on a 2.75m-long guitar shark
caught off Changi by bumboat operator Tan Seck Suah, 54.
The fins of the guitar shark, which was caught in the
waters near Changi Naval Base, was cut up at the Tekong
Seafood Restaurant in Changi Village. Mr Tan Seck Suah, who caught
the shark, sold it to the restaurant for about $600. The shark is
2.75m-long and weighs 100kg. (Why fisherman can get near a
Naval Base and do fishing here?!)
He also claimed to have caught a 100kg giant grouper off Pulau
Tekong three weeks ago.
While it doesn’t happen every day, experts say it is possible for
large sharks to be found in local waters.
Commenting on the report and picture, Mr Anthony Chang, curator
at Underwater World Singapore, said the animal’s appearance
suggests that it belongs to the shark and ray family.
He said: “The cartilaginous fish shown in the picture has
characteristics belonging to members of the genus Rhynchobatus.
They are sometimes called different names, including guitarfish,
wedgefish, guitar shark and shovelnose ray.
“It is not a true shark. It would be more closely related to the
ray and skate group of cartilaginous fishes.”
Cartilaginous fish have internal skeletons made entirely of
cartilage, with no hard bones.
The latest International Union for Conservation of Nature (IUCN)
Red List of Threatened Species lists six species from the
Rhynchobatus genus as vulnerable or endangered, which means they
face a high or very high risk of extinction in the wild.
Mr Chang said such fish are typically warm water tropical marine
species.
“The tropical marine belt is a pretty large area in the ocean.
If this fish was not native to Singapore, it may have come into our
territorial waters.”
Dr Tan Heok Hui, a lecturer at the National University of
Singapore (NUS), said water currents, especially during the monsoon
season, could have brought the fish to Singapore waters.
Endangered
The IUCN website said that such fish are endangered due to
overfishing because their fins are considered to be premium quality
and fetch the highest prices.
Depending on the species’ habitat, some are also threatened by
habitat destruction and pollution, especially in South and
South-east Asia.
Commenting on the catch, Mr Chang said the anatomy of the head
and the position of the mouth make it adapted for bottom
feeding.
But why was it spotted near the water surface as related by Mr
Tan?
Mr Chang said it could have appeared on the surface because it
was chasing prey that had gone up from the sea bed, or it had
detected food on the surface.
“Also, certain diseases such as neurological problems or
parasites may increase the probability of a bottom-dwelling species
moving up to the sea surface,” he said.
Dr Tan said the fish could also have been injured or rose to the
surface as a prelude to breeding.
Mr Chang said such fish are unlikely to attack people, unlike
great white sharks.
“However, any large animal can potentially cause bodily injury
or even death to a human being, especially if it is harassed.
“If you encounter such a fish in the water, you may want to
observe it from a distance. But the safer approach may be to calmly
move away from it, that is, get ashore or return to your boat,” he
said.
A spokesman for the Agri-Food and Veterinary Authority said that
guitarfish is currently not listed under the Convention on
International Trade in Endangered Species of Wild Fauna and Flora
so there’s no law against catching or selling it.
But because the Rhynchobatus species is under threat, Dr Tan and
NUS fish biologist Jeffrey Kwik encourage people to release such
fish if they catch them.
Mr Kwik said: “It’s a shame not to release such large fish back
into the ocean because usually by the time such fish reach this
size, it’s at a stage where it’s able to reproduce and contribute
to the breeding population.”
Dr Tan suggested that recreational anglers take a picture with
their mobile phones if they catch something interesting, before
letting it go.
He said: “Most of these bottom dwelling shark-rays are data
deficient, meaning there is insufficient information about them.
Yet they are caught in the tonnes every year for their meat and
fins.
“So they could be even more critically endangered than what is
currently stated by IUCN.”
Another reason not to eat such large fish is the possibility of
high levels of mercury.
Dr Tan said: “With large predators, they do tend to accumulate
pollutants such as heavy metals.”
