Clam diggers' use of salt to lure prey damaging coastal ecology, conservationists say
Clam diggers may be damaging a Yuen Long coastal mudflat by using salt to draw the molluscs from their burrows.
Conservationists warn that the technique can be detrimental to many other organisms co-existing in the mudflat, but the government's conservation officials say they are powerless to stop the practice.
At Ha Pak Nai, clam diggers have found that they can abandon their digging tools and avoid expending any effort by simply sprinkling salt down the burrows of razor shells to force them to the surface.
Kevin Laurie, who has been doing conservation work at Ha Pak Nai since 2008, said he had never seen the method being used before.
"It just appeared out of nowhere," he said.
Recently, at least 20 people had been using salt to hunt the shells, Laurie said.
He said usual clam-digging activities had already destroyed some seagrass beds, and was concerned the latest technique would inflict even more damage on the ecology.
"This activity is not only leading to the destruction of the seagrass beds, but also poses a direct threat to juvenile horseshoe crabs and other marine life from the effects of sudden high concentrations of salt in the pools and the burrows," he said.
Laurie also believed the method amounted to cruelty to animals.
Dr Paul Shin Kam-shing, of City University's department of biology and chemistry, said the salt would alter the "micro-habitat" instantly, possibly wiping out any organism that could not survive in the increased salinity.
He said tests conducted by one of his students showed saline levels near the holes had surged to 40 parts per 1,000, well above the normal seawater level of 33 parts per 1,000.
"There are many other marine organisms on the tidal mudflat and not all of them can tolerate a sudden rise in salinity," said Shin, who cooperates with the Ocean Park Conservation Foundation on a horseshoe crab programme at the beach.
Samantha Lee Mei-wah, senior marine conservation officer from WWF Hong Kong, said she had never heard of such clam-catching practices before.
Lee wrote to the Agriculture, Fisheries and Conservation Department about the problem and was told there was little it could do since the location was not part of a marine or country park.
The Ha Pak Nai mudflat is not protected by any statutory zoning plan, despite the presence of the endangered horseshoe crab.
The department also told Lee that the clam-hunting method did not breach laws regulating destructive fishing practices.
A department spokesman called on the public to protect the ecosystem and said it would step up publicity and education on environmental protection.