20 March 2011

Dugong sighting at Chek Jawa?

Dr Dan Rittschof and students from Duke University are back for their annual trip to Singapore!
N. Sivasothi kindly arranged for us to visit Chek Jawa. Here he is sharing about the history of this special shore.

Duke University comes every year to do a module studying various aspects of environmental issues in Singapore. Dr Dan has been a strong advocate of Chek Jawa and is involved in among (many) others, projects such as Kok Sheng's study of Chek Jawa after the mass deaths in 2007. During the 2007 incident, there were mass deaths particularly among sea cucumbers, sea anemones and sea stars.

This is also my first intertidal visit to Chek Jawa after the heavy rainfall in late Jan 2011. Has marine life on Chek Jawa been affected by the flooding in Johor?

The tide wasn't very low today, but we still managed to explore a little of Chek Jawa.
As usual, the Duke students are a delight as they are so enthusiastic about our marine life. They found this purple branching sponge (Callyspongia sp.) that was washed ashore, with lots of cephalopod egg capsules among the branches. Here's Dr Dan taking a closer look at it.
I love visiting Chek Jawa with Dr Dan because I learn so much from him. We saw a pair of Coastal horseshoe crabs (Tachypleus gigas) and Dr Dan shows us the special claspers that the male has (in blue circle) that is used to cling onto the back of the female.
The female doesn't have such claspers.
Dr Dan says these hermit crabs that we commonly see on our shores, with one enormously enlarged pincer, are probably from the Family Paguridae.
Wow! The students have found a gianormous crab! It is probably a Mud crab (Scylla sp.) and we seem to be stumble upon these large crabs on Chek Jawa recently. These crabs are usually found in mangroves, so it was odd to see this in the middle of the seagrass meadows. These crabs are commonly eaten as chilli crab. They are also released in religious ceremonies, sadly sometimes in inappropriate places. Such "animal liberation", meant to demonstrate kindness, can ironically be cruel to the animals.
Dr Dan is very good at handling crabs, and manages to gently hold this crab so we could take a closer look at it, without hurting himself or the crab.
In the seagrass meadows, the students discover a huddle of injured fishes that look like they had escaped from the nearby fish farms.
A little Hairy sea hare (Bursatella leachii) is also found. Strangely, this was the only one seen. Usually, these sea hares are seen in large numbers when they are in 'season'. Among the other special sightings was a pretty little Noble volute (Cymbiola nobilis). Unfortunately, we didn't manage to find any large patches of living Button snails (Umbonium vestiarum).
The students are keen on seeing echinoderms and were very good at finding them! We saw Thorny sea cucumbers (Colochirus quadrangularis), Ball sea cucumbers (Phyllophorus sp.), Pink warty sea cucumbers (Cercodemas anceps), Garlic bread sea cucumbers (Holothuria scabra) and Smooth sea cucumbers. We also saw many many Cake sand dollars (Arachnoides placenta).
They also found a tiny Cake sea star (Anthenea aspera)! And several Sand stars (Astropecten sp.).
We saw a number of Haddon's carpet anemones (Stichodactyla haddoni) and they were unbleached. We also saw many happy peacock anemones (Order Ceriantharia).
How delightful to come across several Common sea stars (Archaster typicus) near the boardwalk! There used to be countless Common sea stars on Chek Jawa. They practically disappeared after the mass deaths in 2007. So it's good to see them again.
With the sighting of a broad range of echinoderms and variety of common marine life, I get the sense that the recent flooding in Jan 2011 has not seriously impacted marine life on Chek Jawa. What a relief!

Chek Jawa is home to some seagrasses rarely seen on our other shores. There were small patches of bright green Beccari's seagrass (Halophila beccarii) and the meadow of Smooth Ribbon seagrass (Cymodocea rotundata) seemed fine.
The tide soon turned and as we left, a few of us decided to have a last look at Chek Jawa in the setting sun from the Jejawi Tower.
While we were there, Dr Dan pointed out a large animal swimming in the incoming tide at the northern sand bar! This is the same area where we had seen dugong feeding trails in 2007!
Small sneaky camera doesn't  zoom very well. This is the best shot I have of the mysterious creature. From the wake that was created by the animal, it seemed quite large. Probably about 2m long. The tide was still quite low, so we think it's more likely to be a dugong than some other large animal like a dolphin. More about dugongs in Singapore and dugong sightings.
Wow! What an awesome way to end a great trip to Chek Jawa. We are now motivated to stalk the shore from the Tower during evening incoming tides to see if we can spot the dugong again!

1 comment:

  1. I just realised Dr Dan's shirt looks kinda like a noble volute!



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