Tag Archives: marine biology

Suspected Mui Wo Shark is Actually a Dolphin

Marine police on Saturday (7th May 2016) searching for a shark in Silvermine Bay after a beach-goer reported that he might have seen a shark outside the shark net. The life guards raised the red flag and a police launch and government flying service helicopter were dispatched. But witnesses interviewed by Apple Daily also suggested it may have swum more like a dolphin than a shark. Apple Daily posted a video on their site  here. You can see the “shark” at the 1:00 minute mark. It’s definitely a dolphin.

Extend restricted zone at Lamma turtle beach to keep out junk parties, urge green groups

A wider restricted area in southern Lamma would keep out the noisy junk parties that threaten the nesting site of rare creatures

It’s a sunny September day and half a dozen junks and pleasure boats are anchored in a scenic inlet on southern Lamma Island.
House music is booming and banana boat-tugging speedboats zip across the bay, while those with the energy make the 50-metre swim to shore – unknowingly committing an illegal act by frolicking on the sandy shores of Sham Wan beach.
The beach is one of the few regular nesting sites for endangered green sea turtles in southern China and is a restricted area during the breeding season between June and October. It was designated a site of special scientific interest in 1999.
Illegal entry is liable to a maximum fine of HK$50,000, but that’s only if nature wardens are able to stop such violations.
Scientists and green groups want the Agriculture, Fisheries and Conservation Department to ramp up protection efforts by expanding the 0.5-hectare restricted zone to the entire bay to keep out junk parties.
A study by the Eco-Education and Resources Centre between 2013 and 2015 recorded anywhere between 12 and 17 boats anchored in the bay at weekends. Average noise levels went as high as 80 decibels, similar to a police siren, in some parts of the bay.
Green turtles are known for their migratory behaviour and loyalty to feeding sites and nesting grounds. Tracking efforts show they usually swim to Wanshan Archipelago, Fujian waters, the Pratas Islands, the Spratly Islands and the Philippines after visiting Hong Kong.
“Nesting sea turtles are easily affected by human activity,” said ERC science manager Dr Michelle Cheung Ma-shan.

  

“If a turtle is put off from approaching the beach, it will be forced to lay its eggs underwater, where they will die.”
There have already been notable drops over the years. Between 1998 and 2006, there were 14 records of nesting turtles in Sham Wan. But only two have been documented since 2006, with the last sighting in 2012.
Floating markers similar to ones used in marine parks could be set up to demarcate the entire bay as a protected area.

  

The ultimate goal is to establish a marine park in hopes that strengthened conservation efforts can bring back sea turtles in greater numbers, says Ken Ching See-ho, the ERC’s founder and director.
“The first step is to expand the restricted area under the Wild Animals Protection Ordinance.”
Cheung said nature wardens should be patrolling the beach to keep people out, but their field studies showed they were only present about “60 to 70 per cent of the time”.
Ching said the department could look to successful examples of turtle protection areas overseas, such as the Sandakan Turtle Island Park in Sabah, Malaysia, and a protected area in Taiwan’s Penghu Islands.
Green Power chief executive Dr Man Chi-sam said Hong Kong’s efforts at turtle conservation were “very behind” and “very passive”. “[The findings] also reflect the low public awareness and understanding of this species in Hong Kong,” he said.
A department spokesman said regular patrols were conducted in the area to control unauthorised entry and to monitor the nesting activities of green turtles. “We will step up patrols and put up more warning signs to alert the public not to enter during the restricted period.”

Source: SCMP, 15 Oct 2015

6-Foot Black-Tip Reef Shark Caught by Handline in Victoria Harbour – This Day in 1932

On the 9th of October 1932: a 6 foot 6 inch, 186 lbs black-tip reef shark (Carcharinus melanopterus) was caught by fishermen off th Kowloon Docks (between present day Hung Hom and the Laguna Verde residential blocks). It was caught on a hand line made of hemp with a half-pound snapper as bait on a large iron hook. The fisherman was definitely trying to catch a shark and had a large bait and strong tackle on purpose. The sea was choppy, a fresh N.E. wind was blowing and few small fish were about. The previous week a number of shark were about off Kowloon Docks and on 25th September […] at least 50 snapper were lost through sharks taking them before they had been pulled up to the surface. This particular fish was played 20 minutes, pulled in to within 2 feet of the surface and then harpooned. It was not pulled on board but was lashed to the side of the sam pan. Market value about $7.00 – roughly equal to HKD 2,280  today. Stunning to think that shark was abundant enough locally to cost that little: a whole 6-foot, 84.3 kg black-tip reef shark for only HKD 2,280! Compare this with a recently quoted wholesale price for 1 kg of shark’s fin in Guangzhou (roughly  comparable to the shark discussed here) of USD 960 or HKD 7,480! Why the difference? Rarity. Sharks have become so rare, that the prices are soaring and they face more and more risk of extinction from over fishing.

Decomposing 5m Whale Shark Found Off Cheung Chau With Nylon Rope Around Its Tail

The decomposing body of a whale shark, a rare species in local waters, was found off the coast of Cheung Chau. The five-metre creature was spotted about 50 metres off the island by Cheung Chau resident Dan Carew. He reported the sighting to the police shortly before 7pm yesterday (31st August 2015).

Image: Dan Carew (via SCMP)

The marine police later located the decomposing body near a coastal area off Cheung Chau Peak Road West. Carew told the media he saw the shark floating off the sea at sunset and immediately left his home to check it. It was later washed closer to the coast. Carew said there was a nylon rope around its tail. After studying the pictures and a video provided by Carew, the Ocean Park Conservation Foundation said it was a whale shark, characterised by its square head and pectoral fins.

Image via SCMP

A spokeswoman said the foundation could not tell how it died and would try to learn more from the Agriculture, Fisheries and Conservation Department. He said the largest known extant fish species was rare in local waters, although there had been occasional sightings.

Skin, fat and muscle samples were collected but a necropsy could not be made because of the poor condition of the carcass and the environmental restrictions on- site. AFCD has arranged carcass disposal.

On July 20, a five-metre whale shark was spotted in the sea off Tung Lung Chau in Sai Kung by a local fisherman. It later disappeared. In July 2012, a whale shark was spotted just meters off a popular beach on Lamma.

Footage by Dan Carew published though SCMP TV can be seen here.

Source: SCMP, Apple Daily, AFCD

The Stingrays of Hong Kong

I have just added a page about all the different species of ray that are found in Hong Kong. Here is a little preview on just the stingrays. Check out the full list of rays here.

The Stingrays of Hong Kong:

 

Round ribbontail Ray / Black-spotted stingray (Taeniura meyeni)

Round Ribbontail Ray (via WikiCommons)
Round Ribbontail Ray (via WikiCommons)
A bottom-dwelling inhabitant of lagoons, estuaries, and reefs, generally at a depth of 20–60 m (66–197 ft). Reaching 1.8 m (5.9 ft) across. Generally nocturnal, the round ribbontail ray can be solitary or gregarious, and is an active predator of small, benthic molluscs, crustaceans, and bony fishes. Although not aggressive, if provoked the round ribbontail ray will defend itself with its venomous tail spine. In Hong Kong, it is found mainly in the relatively clear southern and eastern waters, but it has also been found in the northern part of Lantau and in brackish water near the Pearl River estuary. It is also one of the species that has been found on Hong Kong’s artificial reefs. Check out Eric Keung’s spooky photo of a this stingray in Hong Kong waters.
Between July 2005 and June 2008 there were two cases of people being stung by stingrays in HK – fortunately with mild outcomes. The sting and its venom can cause bluish or greyish discoloration around the wound, disproportionate pain, muscle cramp, weakness, seizure, hypotension, cardiovascular toxicity, deep wounds and lacerations. In other words, stingrays are dangerous! Just watch from a distance and don’t touch!


Blue-Spotted Stingray (Neotrygon kuhlii)

Blue-Spotted Stingray, Papua New Guinea (via WikiCommons)
Blue-Spotted Stingray, Papua New Guinea (via WikiCommons)
The body is rhomboidal and green with blue spots with a maximum width estimated at 46.5 centimeters (18.3 in). The rays coloration is a warning for the highly poisonous barbs, thus few animals attempt to overpower this ray. In HK, they are more easily seen in summer in the shallow water along the coast, on coral reefs and in mangrove areas. Because of the venomous sting observers should not get too close or try to touch it!


Pale-edged stingray (Dasyatis zugei)

Pale-edged Stingray (via WikiCommons)
Pale-edged Stingray (via WikiCommons)
A bottom-dwelling ray most commonly found over sandy areas shallower than 100 m (330 ft) and in estuaries. It measures up to 29 cm (11 in) across, has a diamond-shaped pectoral fin disc, a long projecting snout, small eyes, and a whip-like tail. It is chocolate-brown above and white below and feeds mainly on small crustaceans and fishes. In HK it is mainly found in the western Pearl River estuary south of Lantau Island.

The Tai Po Whale of 1914 and the Taipo Whale of 2014

I found another ‘gem’ while looking through old HK newspapers:

A Whale Now!

A reader informs us that a whale 23 feet [7m] in length was seen in Tolo Harbour, near Taipo, on Sunday [11th of May 1914], and that the police, from a launch, fired three rounds at the mighty creature, which however disappeared.”

Taken from the Hong Kong Telegraph 13th of May 1914
Taken from the Hong Kong Telegraph 13th of May 1914
How strange to think that back then the first reaction on seeing a big whale, was to pull out a gun and shoot it!

It struck me as quite interesting, that Tolo Harbor near Taipo was also the site the stranding of a 42-foot (13m) Omura’s whale in March 2014 – almost exactly 100 years later!

Tolo Harbor is almost completely enclosed by land so any whale erring into it is bound to get confused, I think.

Extinct in hong Kong – the Maxima Clam (Tridacna maxima)- ?

The giant clam Tridacna gigas which can grow to 120 in width and 200 kg in weight is one of a group of clams called giant clams – the Tridacnids. Although T. gigas is the biggest of them, there are others which are still pretty huge by clam standards. One of these giant clam species, the Maxima clam Tridacna maxima, used to occur in Hong Kong. It grows to about 40 cm width, though typically is only around 20 cm in width. But consult the IUCN records for this clam species and you will see that although it occurs throughout the tropical and sub-topical waters of the Indian and western Pacific Oceans, the entry for Hong Kong sadly reads ‘regionally extinct’. When did that happen? Why did they vanish? These are the questions I wanted to find answers to.

When did it go ‘regionally extinct’?

The first entry I could find for the Maxima clam being regionally extinct in Hong Kong is 1983. Unfortunately that’s about all I could find. But at it has been gone from Hong Kong since at least 1983. Unless of course it has returned….its a slow-growing animal but has a very wide dispersal through free-floating larvae that live in the plankton – that’s why it occurs over such a wide geographical area spanning nearly a quarter of the planet! So theoretically, if conditions are right (see more below) and larvae are swept over Hong Kong or are purposely introduced by humans, the Maxima clam could reestablish itself in Hong Kong.  So the next question is why did it go extinct in Hong Kong in the first place?

a Maxima clam tucked into some hard coral (via WikiCommons)
a Maxima clam tucked into some hard coral (via WikiCommons)
What happened to the Maxima clam in Hong Kong?

Apart from the fact that the Maxima clam lived on coral reefs in Hong Kong waters, I can not find any more details of how big the population was, which exact areas in inhabited (obviously coral reefs, so that narrows it to Eastern and Southern Hong Kong waters) or whether it was harvested locally. It is however clear that Hong Kong used to be a big regional market for giant clam species in Asia. Giant clams were and still are a delicacy in Asia (mostly the meat big abductor muscle) and the shell was used for decoration (though not extensively). Even the UN Food and Agriculture Organization has no useful fisheries statistics for Tridacnids. So there is no information on how many – if any – were harvested from Hong Kong waters before they disappeared.  The maxima clam like all clams is a filter feeder which suck in water, filters out and swallows edible particles and then ejects the water out again. As such it is quite vulnerable to toxic substances in the water. In addition, it harbors symbiotic microscopic algae called zooxanthellae (zoo-oh-zan-the-lay) in its tissue. These absorb the clams waste  products like CO2 and photosynthesize turning them into sugars in the presence of sunlight and giving off oxygen for the clam.

When open, the bright blue, green or brown mantle of the clam is exposed and obscures the edges of the shell which have prominent distinctive furrows. The attractive colours of the mantle are the result of pigment cells, with a crystalline structure inside. These are thought to protect the clam from the effects of intense sunlight, or to bundle light to enhance photosynthesis of the zooxanthellae.

 

1024px-Coral_reefs
Maxima clams – one open showing the brightly colored mantle, the other closed and only identified by the zig-zag pattern of the shell valves. (via WikiCommons)

This is essentially what corals do, too, which is why they share the same habitat – coral reefs. And like most reef corals the maxima clam also gets most of its nutrients from its zooxanthellae . Coral reefs suffer enormous damage from smothering by sediment that washes into the sea from rivers and rainfall and from clouding of the water and smothering by excessive algal blooms. Both of these were and still are to some extent big problems for Hong Kong waters, whereas in the past this was not the case. Algal blooms and sediment runoff increased a lot as a result of the increase in human population in Hong Kong and as a result of rapid industrialization and the associated water pollution. This combined with harvesting seems to be the most likely reason for the disappearance of the Maxima clam from Hong Kong waters before 1983.

Will there ever be giant clams in Hong Kong again?

I hope so. Like I said earlier, if conditions are right, any of the wide-ranging planktonic larvae of the clam that stray into Hong Kong waters could settle and grow to adulthood. Failing that humans could also try to establish them by attaching cultured juveniles to appropriate spots on reefs – but this is more complicated and costly, although Singapore has attempted this with initial success using another giant clam species Tridacna squamosa. But the main criteria is suitable conditions for a population to establish and grow – in other words we need clean seas again. Hong Kong has improved a lot on this front up until very recently, when the increased coastal development in southern China started to create a lot of water pollution which somewhat diminishes the results. There is still a long way to go. But I would say that divers should keep an eye out. In fact, the ReefCheck 2015 recorder forms even have a section for giant clams (Tridacna sp.), so its not just me that is hopeful! You never know. you could be diving some coral reef in Sai Kung, Tung Ping Chau, Hoi Ha Wan or the Ninepin Islands and come across a maxima clam. It might be an old dead one stuck in a reef with just the wavy outline of the two shell valves (probably) or it could have the fat, bright blue or green mantle of a live clam – in which case 1) hooray for Hong Kong and 2) please report your finding to the AFCD and Reef Check!