13 September 2008

Giant clams eaten to extinction?

In Sabah, giant clams in a reserve were being eaten by workers at a seaweed farm (ok, seaweed farm on a reserve is yet another issue. But let's just consider those clams first).

The Daily Express featured articles about a pile of big Giant clams being slaughtered "for just a meal or two". Those eaten were believed to be 15 years old.
Giant clam (Tridacna squamosa)
Does Singapore have Giant clams? Yes indeed! But how are they doing?

And what is being done about protecting Giant clams elsewhere?

Here's some stuff I found out.

It was noted in the Sabah article, that all Giant clams are listed on CITES Appendix II (which means there are international regulations that apply to the trade in these clams).

In Sabah Tridacna gigas and Tridacna derasa have gone "locally extinct", while Tridacna squamosa "may well be the next species to go extinct".

Fortunately, things are not so dire in Singapore.

Can giant clam (Tridacna squamosa) populations be restored on Singapore's heavily impacted coral reefs? on Wiley InterScience 25 November 2006
by James R. Guest, Peter A. Todd, Eugene Goh, Balasubramaniam S. Sivalonganathan and Konda P. Reddy.

from the abstract ...
Giant clams have been a sustainable resource for millennia, but unregulated harvesting has led to local extinctions within the Indo-Pacific region. Giant clam mariculture can produce large numbers of juveniles for restocking wild populations where natural recruitment is low or absent.

Singapore is surrounded by more than 60 small islands, many with fringing reefs. These reefs, however, experience increased turbidity and sedimentation resulting from massive coastal development projects and regular dredging of shipping lanes.
There are examples of such coastal development projects in the flurry of posts just yesterday...alas.
Seven reefs off Singapore's southern islands were surveyed (9670 m2) for giant clams. Also, an experiment was conducted to determine the growth of Tridacna squamosa reared in aquaria. 144 clams (T. squamosa) were transplanted to four reefs around Singapore to study survival and growth in a heavily impacted environment.

A total of 23 adult clams from three species were found during the survey, representing a mean density of 0.24 per 100 m2. Most clams were found at Raffles Lighthouse, Singapore's best reef. No juvenile clams were encountered.
No baby Giant clams is not good. I must find out what constitutes a baby, because we do see some small giant clams on some of our field trips.
Results suggest that, despite high levels of sedimentation and turbidity on Singapore's reefs, giant clams can survive and grow well. Restocking efforts using maricultured clams may be effective in enhancing the dwindling local populations. It is not clear, however, whether a self-sustaining community can be established as high sedimentation may hinder larval settlement and survival.
Here's one interesting story of success in restoring Giant clams ...
The Clan of the Clam by Dr Richard Chesher on the EarthWatch Institute website

He set out to save the Giant clams. And according to conventional conservation wisdom, he did everything wrong. Yet, he saved the clams while conventional methods failed.

Some extracts...

"The biological solution seemed simple enough: gather remaining big adults, put them into a shallow-water sanctuary where they can breed successfully, and leave them alone.

The first lesson I learned was that if I wanted to try something like this, I would have to do it without any official support.

SPREP, which even then was the established wholesale broker for conservation aid funds to the region, backed off from the idea instantly. They had two problems. First, what would happen if the people stole the clams? And second, what would happen if the larvae of the clams simply floated off to sea, and there was no local recruitment? The project might fail.

Aid projects are not supposed to fail. This is why seminars, workshops, consultant reports, and surveys are favored; they can't fail.

Dr Richard Chesher's approach: I was not friendly. I refused to go to feasts. I did not accept any of the invitations of friendships with local individuals or families. I didn't go to people's homes. I didn't pay any local people to do anything. I studied clams with the express purpose of watching the people of Vavau extinguish a valuable species."
I am quite heartened by his story. For me the main takeaway is that ordinary people must first believe it is in their own interest before protection can be sustainable.

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