May 19, 2008

High on Sisters

The tide wasn't very low today but it was a public holiday so we headed out for Sisters Island for a sloshy trip in the wee hours of 3am.
At the high water mark, as we waited for the tide to go down, there were lots of beautiful Pechia anemones (Peachia sp.). YC and I start to miss Dr Daphne as we encounter the nems.This small anemone has only one ring of about 16 tentacles. Often seen is a structure of 3-5 bumps in the middle of the mouth that protrudes out of the mouth. This sea anemone is more often sighted at our Northern shores, although possibly we just never take the time to look for them on our Southern shores.

When the tide is high, it's a great chance to look for fishes. And they are generally less shy at night.

The shores are teeming with little gobies.
The Shadow goby (Acentrogobius nebulosus) is commonly seen in shallow pools. It has three large dark brown blotches on the sides of the body (not easily seen from the top). It is poisonous to eat as it contains tetrodotoxin (the same toxin found in pufferfishes) in its flesh and internal organs. In some places, it is called the Poisonous goby. This is probably why the fish is not as shy as other gobies.

The larger Ornate lagoon-goby (Istigobius ornatus) is another goby commonly seen on many of our shores. It has a bulbous snout that overhangs the mouth, with two rows of deep blue spots on the lower sides (not easily seen from the top).There are lots of other pretty little gobies, like this one. I have no idea what it is.
The beautiful Head-stripe goby (Amblygobius stethophthalmus) is generally only seen near reefs and I saw one in a quiet pool near the corals as the tide went down. There is a dark stripe edged with pale blue on the side of the body through the eye to just past the gill cover (not easily seen when viewing the fish from above). There are bright spots and markings on its head. It makes its burrow under solid objects.
Blending in with the coral rubble was this little filefish (Family Monacanthidae) with a frilly long dorsal spine at the top of its head, and bristles near the tail. The single stiff dorsal spine gives this family of fishes its scientific name: 'mono' means 'one' and 'canthus' means 'thorn'. The common name comes from the texture of its skin. The scales are small and have prickles on them. So the skin feels leathery and rough, like sandpaper.The shore was also teeming with Whitings (Sillago sp., Family Sillaginidae). These long, slender silvery fishes have a torpedo-shaped body, large eyes and small mouth on a conical, sharp snout. In Singapore, this fish is also called 'pasir', which means 'sand' in Malay. The species are difficult to tell apart in the field.
Lurking among the rubble was this colourful fish that disappeared as soon as I took a photo. I have no idea what it is, it might possibly be some sort of grouper.In the calm shallow lagoon of Sisters, we almost always see the Fringe-eyed flathead (Cymbacephalus nematophthalmus). It is superbly camouflaged and I nearly stepped on him! It has bony ridges on the head with spines, 7-8 dusky bars on the back and sides and its fins has variegated patterns.But it's most endearing feature is those golden lashes! What girl wouldn't want to have those. These fringes are 6-9 skin tentacles over the eye. This predator feeds on creatures that live on the sea bottom.

Sisters has among our best reefs that are easily accessible to the public. The swimming lagoon in some parts are crowded with all kinds of animals. Here, two hard corals (purple and brown) and a soft coral (green).The brown hard coral (possibly Porites sp.) had a tiny fan worm living in it! The green feathery animals are probably soft corals because they have branched tentacles. But I have no idea what it is.

At night, our corals expand their polyps and no longer look like lumps of rock!Each hard coral is a colony of tiny animals called polyps. Each polyp creates a hard skeleton for itself. With the tentacles of the polyps extended, the colony takes on amazing colours and textures.
The polyps look like tiny sea anemones, with a ring of tentacles around a central mouth.As corals are identified by the skeleton structure, it's hard to identify the species of a living coral especially when the skeleton is hidden by thick tissue and 'blooming' polyps. I don't know why some of the polyps on this hard skeleton had white parts.Here are the very tiny polyps of a branching coral (possibly Montipora sp.).The branching Acropora corals (Acropora sp.) are always a special find as they are rather rarely seen on our accessible reefs. Acropora hard coral have a large corallite at the tip of each branch called the axial corallite. New corallites (called secondary or radial corallites) bud off along the sides while the axial corallite continues to grow upwards on the tip of the branch.Branching corals are a great hiding place for small animals. This particular coral had tiny crabs and little clams tucked among its branches.

Sponges are a great place to hide away too.All regular shore explorers know this commonly encountered brown sponge is usually riddled with tiny brittlestars, each only sticking out its little arms from the holes in the sponge.If you take a closer look though, you might spot other little fan-like things sticking out of some of the holes (photo on the right). I have no idea what they are. Seems a little too fine for fan worms. Could these be the feeding tentacles of barnacles? Hmm.I also chanced upon a beautiful pink version of this sea anemone. Bluish ones are more commonly seen. We still don't know what this sea anemone is. Some field guidebooks call anemones that look like this Condylactis, but Dr Daphne says they are not. Thus we usually call it Condylactis-NOT. The sea anemone has one ring of about 20 tentacles. Most of the tentacles are usually held flat against the surface, arranged in pairs or sets of three. Often, 5 of the tentacles are held upright forming a 'tent' over the mouth. The mouth is often seen upturned.

Chay Hoon of course shares the fabulous find of the day.A beautiful moon snail with a delightful shell pattern that reminds me of the patterns on coffee-cake! The front part of the body is brown with three white stripes.She found two of them on coral rubble. They were quite tiny, the shell about 1-2cm. But I have seen a larger one on St. John's in the past. These moon snails move very fast.The 'door' of the shell (called operculum) is white and made of shell (and not a brown horn-like material like the more common Polinices sp. moonsnails). I don't know that these moon snails are as they don't appear in any of the guidebooks that I have.We also observed that BOTH snails had a little snail shell on its butt! Is it excreting the shell after eating the snail? Wow. So much more to learn about our shores.

I didn't venture out as far into the deeper waters as it's hard to take good photos in deep water. And the wind kept the water surface ruffled. But the rest made the brave foray and encountered more wonderful fishes, octopus, flatworms, rare crabs and saw a lovely giant clam. Read more about their finds in the links to their blogs below.

As the moon set and dawn broke, the tide came in. The ravenous team swarmed over breakfast in a blur of furious feeding.Well fed and ready to go home, the sun finally peeked over St. John's, prompting lots of photo-taking.Sisters Island is open for camping (with a permit from Sentosa). Since it was a long holiday weekend, we weren't surprised to see campers on the island.There was a family with kids and two dogs in their tents facing the big lagoon.And another group of fishing folks near the jetty.As we left, they had already set up their fishing for the day.Sisters Island also has wild Long-tailed macaques (Macaca fascicularis). They used to be only found on Big Sisters Island, but recently some are also found on Little Sisters Island.The combination of people and monkey is seldom good. Alas, the trash bins at Sisters cannot keep the monkeys out. And all the contents are strewn all over the beach. Including dangerous marine litter such as plastic bags and styrofoam that can choke and kill marine life such as sea turtles.

Perhaps visitors to Sisters Island should take back their trash? This is what we always do on all our trips.

Here's a few of the happy team as we head home away from the pair of Islands. Kok Sheng is still hard at work taking photos. Jerald seems to have enjoyed his maiden trip to Sisters. While the Evelyn the Weather Witch seems to have lost her magic over the clouds. We were blessed with fine weather today. But still, we are wary when she joins us for our trips.

More blog entries about this trip
Sleepy human, lively Sisters on Kok Sheng's wonderful creations blog: lots more sightings in the not so low tide at Sisters.
Swinging by the Sisters on Marcus' budak blog, a poetic rendition of the trip with fabulous photos.


YC said...

oh my a PINK condy-not? ive never seen them before! you think its same as the other condy-nots?

Anonymous said...

Moonsnail looks like Tanea aerolata (RECLUZ, 1844)

Anonymous said...

Should be 'areolata'

Ria Tan said...

Thank you for the id for this moon snail and the other one we saw at Changi!

I had some feeling it might be Tanea but wasn't sure about the distinguishing features for Tanea, as compared to Natica especially.

Ria Tan said...

YC, yes it was pink! I've seen pink ones before, but not very often. Also dark greenish ones.

Only Dr Daphne can help us learn whether they're all the same.

It'll be exciting to find out when she comes to visit us again.