11 July 2012

Giant clams in Singapore and how to save them

Giant clams have been found in Singapore since the 14th century! But our clams are now threatened. What is being done to conserve them?
An awesome paper "Giant clams in Singapore: History, research and conservation" has just been published in the Raffles Bulletin of Zoology that shares archaeological finds of giant clams, recent surveys as well on going efforts to conserve these magnificent bivalves.

From the paper I learnt that more about history of Singapore's giant clams. Which kinds were found in the past and how people used them. Archaeological excavations found giant clam shells at sites along Singapore River and the former coastline such as Pulau Saigon, Empress Place, the Parliament House Complex and St Andrew’s Cathedral! The early inhabitants of modern Singapore relied heavily on fishing and collection of shells to provide sustenance.

There now exists a substantial giant clam research base in Singapore. Work done to date covers both basic and applied research; aquaria and field-based studies. It is known that, at least for T. squamosa, giant clams can survive on local reefs, even under their present, heavily sedimented conditions.

The substantial research conducted on giant clams in Singapore has provided the baseline knowledge and strategic framework for the current restocking plans. If these succeed, hundreds of mature clams will become established on Singapore's reefs, returning them to a state they have not experienced for the last two centuries. That surely would be awesome!!

From the abstract: This review presents the history of giant clams (S.F. Tridacninae) in Singapore as derived from artifacts, primary and grey literature, museum collections, and anecdotal evidence. Archaeological finds from the 14th century include giant clam valves of at least two species: Tridacna crocea (Lamarck, 1819) and T. squamosa (Lamarck, 1819). An 1847 publication lists T. gigas (Linnaeus, 1758) in Singapore, a species that is absent from later inventories. Hippopus hippopus (Linnaeus, 1758) and T. maxima (Röding, 1798) also used to be found on the reefs surrounding Singapore’s Southern Islands, bringing the total number of recorded species to five. Early literature describes how inhabitants of 19th century Singapore relied heavily on fishing and collection of shells for food and trade and that this activity was already impacting clam stocks. Exploitation was probably the main cause of giant clam decline until the 1960s when intense coastal development became an additional contributor. Contemporary surveys of 29 reef sites show very low densities of T. crocea and T. squamosa and a complete absence of H. hippopus, T. gigas, and T. maxima. Very little research was conducted on giant clams in Singapore until 1998 when a mariculture project was initiated. This was succeeded by a programme of basic research that produced papers on mariculture, behaviour, shell morphology, reproduction, and conservation; here we present an outline of some of the more important findings. Finally, we discuss conservation strategies designed to ensure that giant clams will not disappear from Singapore’s reefs altogether.
Read more in Giant clams (Mollusca: Bivalvia: Tridacninae) in Singapore: History, research and conservation. M. L. Neo and Peter A. Todd.  [pdf, 1.07 MB]

Here's Mei Lin (aka Giant Clam Girl) with a small Giant clam, with Jose Hong who wrote an article about Mei Lin's work for the Straits Times.
Clam hunt at Terumbu Pempang Tengah in April 2012
The team have been helping out Mei Lin with surveys for Giant clams for some time. We are astonished to find them everywhere. Like this large one found just in front of the Semakau Landfill (the seawall on the horizon). Kareen is working with Mei Lin on propagating these bivalves so that their offspring can be put back onto our reefs.
Clam hunt at Terumbu Semakau in May 2012
It's great to know about the hard work that scientists are putting in to learn about, protect and conserve these magnificent bivalves in Singapore!

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