Monitoring our giant clams on Singapore’s reefs

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Seascape of Pulau Jong – One of the last remaining (almost) untouched fringing reefs in Singapore.

HAPPY EARTH DAY!

To celebrate this special day (I didn’t realised that I had picked an ‘auspicious’ date), the Giant Clam team organised a fieldtrip to Pulau Jong to monitor the health of Mama Jong Clam – the individual that was taken back to the facility for spawning. Due to past poor experiences with our adult broodstock, we were worried that Mama Jong may not recover and survive in the wild again, despite the intensive care routine that we had provided her prior to sending her back home to the island.

Alas! We all breathed a sigh of relief when we found her 1) alive and 2) looking healthy; albeit that she had moved slightly from her position. Prior to sending her back home, Mama Jong exhibited good signs of health – on the left picture, you can see a distinct white margins along the mantle edges: an obvious sign that the animal is growing healthily. On this trip, those white margins have been fouled and covered with scum, but where her mantle tissue lies the internal shell edges remain white. Ambert who first found her also remarked that her mantle tissues were actually extended out of the shells. It is also very obvious in the photos (below) that she lost her beautiful ‘red’ coat and replaced with a ‘brown’ coat!

Mama Jong is a very special clam for me, as she is the very first wild giant clam during my early encounters of intertidal reef walk. To actually have monitored her over the past 8 years have been immensely fulfilling – knowing full well that their lives are always at risk – bleaching, ship wakes, ship groundings, sediment pollution, diseases, etc… There is a great sense of gratitude to know that she is literally the ‘survival of the fittest’ thus far – a beacon amidst the dark waters, and that our reefs are truly amazing despite its urbanisation.

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Mama Jong Clam: (L) August 2014; (R) April 2015

In addition, we found a fellow clam companion for Mama Jong! Ria was trudging along the shore and that’s when she spotted this reflective white margins! Normally, these clams are very difficult to find due to their well-camouflaged shells. These shells can harbour numerous flora and fauna, which in turn allows the clams to blend in to its environment. What’s amazing is that despite walking along the same shore for the past 8 years, we still miss out some clams! Judging from the size, this individual appears to be ~5-7 years old – possibly a new recruit! With the numerous sightings of younger clams, it is timely to augment my population genetics data with new sequences.

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Jong Clam #3

Another common species in Singapore is the Tridacna crocea clam, but we have so far failed to locate any on Pulau Jong. Today, Ambert pointed out two dead valves from T. crocea.

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Tridacna crocea – dead shell valves

Meanwhile, things on the hatchery are looking good so far… Mama Jong babies are growing happily in our well-conditioned tanks. After almost 11 months (time flies!), some of the larger ones have reached close to 3cm! We have been very careful with this batch, and are hoping that our current routine can help reduce mortality. Our most recent concern would be the spike in seawater temperatures in the aquaria. Presently, we have noticed some bleaching but not widespread. Hopefully, these babies can acclimate to the rapid spikes!

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Babies of Mama Jong – 11 months old

We are happy to see that with extra care and love for our adult clams, we can rehabilitate them back to the wild. With this small success, it gives us more confidence that our breeding programme can yield not only local genotyped babies, but also can become sustainable in the longer term.

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All smiles with the giant clam! Photo credits to Ria Tan.
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One thought on “Monitoring our giant clams on Singapore’s reefs

  1. Hi meilin, am Jack here do ya research centre have any volunteer program for the giant clams as am a marine tank enthusiasm & am keeping sps corals.

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