19 September 2009

Lost Giant clam at Sisters Island

It's the very absolute last morning low tide of the year and we've off to look for Giant clams with Mei Lin.I saw this lovely Fluted giant clam (Tridacna squamosa) in 2004.

But alas, though we looked in the vicinity, it was not to be found. The shore was thick with Sargassum seaweed (Sargassum sp), so we're hoping it was just covered in the seaweed and not really gone. Sigh. Fortunately, Kok Sheng managed to show Mei Lin the baby Giant clam that he had seen on an earlier trip and taken the GPS coordinates of. So her trip wasn't wasted. See Kok Sheng's blog for a photo of this clam. Mei Lin is right, we'll probably have better luck looking for clams in daylight.

But in the Giant clam search, we came across a patch of reef that was just thick with life! There were lots of large boulder corals, jammed with sponges and all kinds of other animals. I noticed the many colonies of Blue corals (Heliopora coerulea) because I remember the Giant clam was near such a colony.

Some parts of the shore was completely covered in living animals! In this photo are clockwise from left: A corallimorph, a baby blue sponge (Lendenfeldia cf. chondrodes), and polyps of an Anemone hard coral (Goniopora sp.).
There were also lots of leathery soft corals (Family Alcyoniidae) of all shapes and sizes.
It was impossible to walk there without killing anything, so I skirted the edges. Corals are living animals and they take a long time to grow. It is bad to step on living corals.

There were the usual commonly seen corals such as Favid corals (Family Faviidae) in the top row, and a nice Carnation coral (Pectinia sp.) as well as Mushroom corals (Family Fungiidae). Kok Sheng was much braver and went to the reef edge and saw vast stretches of a plate-like coral.
In the dark, the coral polyps have their tentacles out! This one looks like a Favid coral with hexagonal corallites in columns.
And here's a Brain coral (Family Mussidae) which usually seems just smooth and fleshy. But at night, you can sometimes see their tentacles.
In the big lagoon were lots of branching Montipora corals (Montipora sp.) and some of them had pretty pink tips. These corals have tiny tiny polyps that look like miniature daisies.
There were also many colonies of Acropora corals with rather stumpy branches (Acropora sp.). These corals are like stony trees and animals may shelter in their branches, such as these little clams.
Indeed, the reefs are home to many animals but it is not always easy to spot them. I saw this animal from afar. Can you see it?
Here's a closer look at it! Octopuses are very common on our reefs but usually well camouflaged. I saw four of them busy foraging. There were also some speedy squids zooming off into deeper water.
Also aways off in the distance, I saw a rather large shrimp. And from my poor photograph, it appears to be the Saron shrimp that I also saw at Tanah Merah yesterday!
Many tiny animals wander about on the hard corals and other immobile animals on the reef. Like these countless little Red-nose shrimps (Periclimenes sp.).
There was this little red feather star (Class Crinoidea) clinging onto a hard coral with its claw-like appendages on the underside of its ring of feathery arms. I gave sneaky cam a little dip, but she didn't take a very good photo of it. Kok Sheng saw several other kinds of feather stars too, see his blog for great photos of them.Other animals are well camouflaged, not by being drab but matching the riot of colours on the reef. This very hairy hermit crab had a shell covered with the pink encrusting algae that made the reef look like a Hello Kitty shop.
I also saw this hairy and colourful crab with bright pink eyes. Kok Sheng and Mei Lin saw another similar one too. It does look like the Red-eyed reef crab (Eriphia ferox). But I'm not too sure, and it might be something else. I saw something similar at Raffles Lighthouse.
Wedged in another crevice was this Bubble-tip sea anemone (Entacmea quadricolor). I didn't see any Tomato anemenonefish (Amphiprion frenatus) that usually live in these sea anemones.
But I did see several Giant carpet anemones (Stichodactyla gigantea) with lots of False clown anemonefishes (Amphiprion ocellaris). The pretty anemone often has a brightly coloured underside with bright pink spots in stripes along its body column.
But it is the clown anemonefishes that get our attention. They are very wriggly and need patience to photograph. I was in a hurry to find clams, so just took some quick shots. The bigger fishes in particular tend to hide under the anemone. Kok Sheng and Geraldine got much better photos of these fishes on their blogs.
There were also lots of corallimorphs (Order Corallimorphoria) on the shores. There were a lot of these ones that look like carpets, in various shades of blue, green, beige.
Corallimorphs (Order Corallimorphoria) are not true sea anemones which belong to Order Actiniaria. When exposed out of water, corallimorphs can pucker up: tucking their oral disk into the body column. Sometimes they are covered with tiny little brown Acoel flatworms.
Other corallimorphs include those with a fringed and frilly edge.
There were also many zoanthids (Order Zoanthidea) on the reefs, although not in overwhelming numbers.

Of course a reef trip is not complete without some sightings of nudibranchs. Although we missed Chay Hoon today, we did see some common nudibranchs like the blue spotted Phyllidiella pustolosa which Kok Sheng found, and the pink spotted Phyllidiella nigra.
And there were also flatworms. The very large spotted black flatworm (Acanthozoon sp.) is very common on our reefs, and we saw several of the blue flatworm with the stripe in the middle of its body (Pseudoceros bifurcus).
Also with us today were Ivan and Nanthini to look for the Frilly anemones (Phymanthus sp.). There were lots of these anemones on this shore in various shapes and colours. Ivan is studying these anemones, and his work will help us understand whether these are different species or not.
We had to make a quick trip of it as the tide window was short. I made a quick check of the outer reef at the bigger lagoon, but didn't get to check out the big lagoon itself. While the reefs on the southern side seemed in good shape, the big lagoon seemed to be less lively. There has been extensive sedimentation and the lagoon has become shallow and silty. There doesn't seem to be the variety and numbers of hard corals that we used to see in the past.

As the tide came in, I checked out the higher shores. The Haddon's carpet anemones (Stichodactyla haddoni) were still there though I didn't see any anemone shrimps in them.
As usual, I got annoyed and frustrated by sightings of empty shells of interesting snails like the Bonnet snail (Family Cassidae) and Cone snail. We have yet to see a living Cone snail on our shores. Which might not be a bad thing as they are highly venomous.
For the first time on this shore, I saw fiddler crabs (Uca spp.)! Does this have anything to do with the increasing sedimentation in the lagoon?
I'm not quite sure what kind of fiddlers these are. The one on the left seems to be an Orange fiddler crab (Uca vocans), but one of them had crisscrossed claws on its enlarged pincer.
As we headed home shortly after sunrise, a group of fishermen were just starting up for a day of fishing on the jetty.
And there sure are a lot of fishes here. The reef right next to the jetty is rich and there's even lots of colourful corals and sponges on the jetty legs. The orange stuff looks like Cave corals (Tubastrea sp.). Kok Sheng has much better photos of this on his blog.
The reef at Big Sisters seem to be changing, but parts of it are still very much alive. We must keep coming back to check up on these little islands.

Thank goodness we had good weather and that the tides were as predicted. Let's hope our luck holds out as we go for our first evening tide of the year tomorrow.

More blog posts about this trip


  1. The Montipora corals look more like Porites to me, but it's hard to tell - they can look very similar. Was the coral brittle (Montipora)or did it feel firm and solid (Porites)?

    Cheers, Jeff

  2. Hey, thanks for that Jeff!

    I didn't feel the coral unfortunately.



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