28 July 2012

Bivalve Big Picture: Bivalve Workshop Day 4

People and bivalves interact in all kinds of ways. Bivalves are food and produce pretty things like pearls that support communities, while people in turn can mess up bivalves and the environment.
On this final day of the Bivalve Workshop, I learnt more about the efforts to understand these issues and the importance of bivalve identification in properly managing them.

Although tiny and immobile, some bivalves travel thousands of kilometers to places where they ought not to be. Through the ballast water carried by huge ships, and on the encrustations on boats of all kinds. Settling on new shores, they are often unnoticed until they cause problems for people, whereupon they are considered invasive aliens. In Singapore, there are few identified introduced marine species. Is this real or because we don't know enough about our native marine life?
Dr Tan Koh Siang of the Tropical Marine Science Institute shared this and other many complex issues surrounding invasive bivalves around the world, during his last lecture in the Introduction to Tropical Bivalves Workshop. Identification of the alien bivalves is important and particularly tricky because a global view is necessary. Here's more about invasive aliens in Singapore.
I also learnt a lot from the talk by Dr Sigit Diwono on bivalves in aquaculture. I didn't realise there was such a vast variety of bivalves being farmed all over the world. From New Zealand and Chile, Australia to China, and of course in Southeast Asia. Although I had a glimpse of this variety on our impromptu survey of bivalves sold at Giant supermarket the day before.
Dr Sigit gave an excellent overview of some of the many ways these bivalves are cultured. And some of the issues faced in the business. Among them, the threat of pollution and theft!
Dr Sigit also gave an insight into how 'see ham' or blood cockles are 'farmed'. Actually, farmers merely harvest an area of shallow mudflat near mangroves. One man can both drive the boat and dredge up the cockles at the same time! The mesh of the dredge picks up only market-sized cockles, leaving smaller ones to grow up. The method is quite sustainable and doesn't impact the habitat too much.
Dr Sigit also shared more about how pearls are farmed. Of course, pearls form within specific oysters. The farmer needs to raise baby pearl oysters from scratch, and look after them for months until they are large enough.
Then special equipment and care is taken to insert a nucleus into the pearl oyster at the right time and right place. After more months of care, a lustrous pearl is produced by the oyster! The oysters are treated with loving tender care at all times because they are precious. For example, they wait patiently for the oyster to open up by itself when inserting the nucleus, so as to avoid damaging the shell.
Mei Lin (aka Giant Clam Girl) and Kareen also enthralled with presentations about their work on Giant clams. Mei Lin shared more about these awesome animals and why it is important to reintroduce them to our reefs.
Mei Lin has done lots of work on Giant clams, finding out more about their social and natural history in Singapore, surveying for them on our shores and finding out more about their ecology and biology. Sadly, although we still have many Giant clams, they are now very sparse and probably can't mate effectively to produce babies to settle on our reefs. This is why Mei Lin's and Kareen's work to raise baby clams and return them to our reefs is so exciting.
To decide the best places to relocate Giant clams on Singapore's shores, Mei Lin also studied how the larvae of Giant clams are dispersed to our waters. In this way, hopefully, our Giant clams can naturally repopulate our islands and submerged reefs!
Kareen then shared more about the work to collect some mama and papa clams from our shores for the breeding project. I was glad to be a part of their trips to Sisters Island, Terumbu Pempang Tengah, Beting Bemban Besar, Terumbu Bemban and Terumbu Semakau.
At the TMSI St. John's Island facilities, the mama and papa Giant clams mate and produce bazillions of babies!
A lot of hard work is involved to keep these babies happy and healthy. With tender loving care, they change from a bunch of cells to swimming larvae, then to a teeny tiny clam with shell and foot. More care is needed to allow them to grow up. The mortality rate is high, but still, hundreds survive. I'm really looking forward to the positive results of this wonderful effort.
The highlight of the finale are presentations by the scientists who participated in the workshop. Each had selected a bivalve to identify and I learnt a lot from their presentations. Even bivalves that we commonly enjoy in our meals are sometimes tricky to identify!
Shells of different species can look very similar on the outside. It is important to take a look at the inside for more clues on the identity of the bivalve. This is why a general photo of just the shell is often not helpful in coming up with a positive identification. We need the 'dead body' so that we can look at the internal parts. This is why specimens are collected for biodiversity surveys like the Mega Marine Survey.
We need to take note of the shape and colour of internal body parts.
We often need to take a really close look at things like the gills of a bivalve. What a great photo of the fine fillibranch gills of this bivalve.
Detailed drawings are often better than photos in highlighting some of the important internal features.
Books and other references help to narrow down the identification. It's like figuring out a puzzle from clues.
Even some of our most common bivalves are tricky to identify based on existing reference materials. Lots more work is needed to sort out the ID of bivalves!
In the process of trying to identify the clams, all kinds of animals were found living inside the bivalves! Like this tiny crab!
Weird white wormy creatures were seen in this bivalve.
Here's a closer look at the worm. There's so much more to discover about bivalves!
In between the lectures, there is lots of time to catch up with everyone, eat delicious snacks, enjoy a great lunch and also check out the touch pool of marine life which never fails to fascinate us.
There were of course many live bivalves in the touch pool. The resident hermit crabs and Drill snails were busy attacking some of the clams!
While waiting to leave the mainland earlier in the morning, we observed a flock of Terns hunting in the sea just off the jetty. The energetic little white birds hover over the water, plunge in and then fly out of the water as they hunt for small fishes.
On the way to the TMSI facility, Marcus showed me a huge eagle's nest!
As we waited for the ferry ride home, we looked at all kinds of snails, crabs clambering on the sea walls. Marcus noticed this sea cucumber. It looks like a Durian sea cucumber (Stichopus horrens) my first time seeing it on St. John's Island!
My only disappointment is that I didn't get to see a single dolphin during the many trips to and from St. John's Island. The only sign of one was on the Island's notice board, sharing about the TMSI effort to gather public sightings of marine mammals in Singapore.
I had a really great time at the Workshop and learnt so much from Dr Tan, the many lecturers and participants who shared more about amazing bivalves. Thank you to the kind hospitality of everyone at TMSI! Here's our last group photo at the end of the Workshop.
I'm already missing bivalves. Low spring tide trips start again next week. Time to put all this newfound knowledge to action and find more bivalves on our shores!

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