Semakau Walk on 19 Sep 2009

Finally, I did not have to do the coordination work for our Semakau walks, and could guide this time round!

I had not guided a public group for like the longest time. Felt really good to be back guiding. I had a pleasant surprise when I saw my group though - 2 of them were from my NS battalion - 1 Guards!


Here's a shot of the group at the recreation area of the island. Our group name was Jellyfish, but unfortunately, we didn't see any jellyfish today. It was only at the end of the trip when the other groups told me there was huge jellyfish near the exit of the secondary forest, and we missed it!


Anyway, we had a tour of the landfill, followed by a video presentation on how the landfill operate, before heading to the intertidal area. Apart from the mosquitoes, the first animal we encountered was this cute little Soldier Crab (Dotilla myctiroides). Sometimes, you could see a whole troop of them crawling over the sand, thus earning them their common name. This scene is no longer that common in Singapore though, and I have only seen it on some of our offshore islands.


Another crab we saw was this Porcelain Fildler Crab (Uca annulipes). A male fiddler crab has an enlarged claw, and as it waves the claw to attract the females, it looked like it's playing a fiddle.


There was a little Mangrove Horsehoe Crab (Carcinoscopius rotundicauda) not too far away from the fiddler crabs. It was, however, not a crab despite the name. Horseshoe crabs are more closely related to spiders and scorpions. They are very ancient animals, and have existed for more than 400 million years!


We saw lots of sponges coming in different colours as we walked on. Interestingly, among these sponges, I saw a pair of Wandering Cowrie (Cypraea errones). Cowries have very smooth and glossy shells, and are often collected to be made into shell boxes or decorative products. Fortunately this is not so rampant in Singapore, and thus we could still see many of them.


We saw a total of three flatworms today, including one above, which is probably a Pseudobiceros stellae. Flatworms, being very flat, are very fragile, and tear easily. Fortunately, they are able to regenerate lost body parts.


Even before we crossed the seagrass meadow, I spotted a Synaptid Sea Cucumber (Family Synaptidae). This sea cucumber was often mistaken for a worm as it was quite long and skinny.


As I was crossing the seagrass meadow, I spotted this Spider Conch (Lambis lambis) among the seagrasses. This animal is certainly a master of camouflage!


Here's the gang crossing the seagrass meadow :)


Immediately after we crossed the seagrass meadow, we saw that the hunter-seekers had found us a few Sandfish Sea Cucumbers (Holothuria scabra). This sea cucumber is the one we usually find in Chinese restaurants. They must be properly treated to remove toxins in them before they can be consumed though.


There's a Gigantic Carpet Anemone (Stichodactyla gigantea) with an Anemone Shrimp (Periclimenes brevicarpalis). We did not find any clownfish on this one though. Anemones have stinging tentacles to sting and capture their prey, but the Anemone Shrimp coats itself with mucus produced by the anemone, and thus is not stung by it. The shrimp will feed on left over food from the anemone, and get protection from predators by living in the anemone. The latter, on the other hand, can do with or without the shrimp.


Moving on, we soon reached an area full of Sand-sifting Sea Stars (Archaster typicus)! This sea star is probably the most common intertidal species one found in Singapore, and we have seen them on most of the southern islands that we have visited. It can burrow into the sand and feed on tiny organic particles found inside.


The hunter-seekers found this Blue-spotted Fantail Ray (Taeniura lymma) among the seagrass. Stingrays have venomous spines on their tails, and can give very painful stings.


And today was certainly a very starry day, as we saw 2 juvenile Cushion Stars (Culcita novaeguineae). We have been spotting several juvenile Cushion Stars regularly during our trips here. It's certainly a good sign indicating that they are reproducing!


Here's the other one we saw. Cushion Stars feed on corals, and can grow to about 25-30cm wide! These juvenile were less than 10cm wide though.


Hairy Crabs (Pilumnus vespertilio) were really abundant here, but as it was able to blend into the surrounding sand and rocks so well, it could be rather hard to spot them sometimes when they were not moving. Mind you, these are not the edible hairy crabs you find in restaurants though, and are in fact mildly poisonous.


We moved to the next station and saw this Stonefish Sea Cucumber (Actinopyga lecanora). It's rather smooth with mottled patterns - looking just like a piece of well-eroded stone!


And once again, we saw the unidentified sea star! We first saw this sea star during the launch of Project Semakau, and so far the experts I had asked had not been able to give me a answer on its identity.


This six-armed Knobbly Sea Star (Protoreaster nodosus) has be spotted around the same area for the past few months! Semakau is one of those few places in Singapore that the public can easily see this charismatic sea star. They usually come with 5 arms, so this one was a little special.


The top animals for me for this trip, however, was this really cute cuttlefish (Order Sepiida)! This was my first time seeing a cuttlefish on Semakau! Previously, I had only seen cuttlefish on our northern shores, though some of my friends had seen them while diving around our Southern Islands. This cuttlefish we saw was rather small - about 5cm long perhaps.


As we headed towards the reef crest, we came across 3 other bigger Knobbly Sea Stars!


The tide was already rather high by the time we reached the reef crest, but fortunately, we still managed to see the resident Fluted Giant Clam (Tridacna squamosa). This is probably the biggest clam species in Singapore, and the one here is about 40cm wide!


Not too far away was this huge Ocellated Sea Cucumber (Stichopus ocellatus). The many "eyespots" on its back were believed to possess some sensory functions or to help the sea cucumber move around or hold to the substrate.


Near the reef crest, there were several huge colonies of hard corals, that were probably hundreds of years' old!


As we were heading back from the reef crest, we saw a Black Long-spined Sea Urchin (Diadema setosum). It has long, venomous spines, which you certainly don't want to touch with bare skin, as the spines are also very brittle. They can break easily and pierce through your skin, causing pain and swelling.


It was nice to see many of the Tape Seagrass (Enhalus acoroides) blooming. The above was a female flower, and in the middle, you could see a small white patch - that's a male flower which has got itself stuck to the female flower. This was certainly pollination in action.


Here's one of the bracts which was holding the male flowers. There were still several male flowers inside, looking like floating styrofoam bits! Seagrass probably has the largest stretch of Tape Seagrass in Singapore. Seagrasses are very important as they provide lots of food and shelter for juvenile animals. Like the trees on land, they also help to return oxygen into the atmosphere as they photosynthesize.


I especially like evening walk because we usually saw more octopuses. This trip, we saw 3 of them. These smart animals are also really good at hiding and camouflaging themselves. Can you spot the one in the above photo?


On our way back towards the seagrass meadow, I spotted this pretty fish stranded in a small tidal pool. Had initially thought it looked like some kind of damselfish, but a quick check with my books revealed it to be a Yellow Soapfish (Diploprion bifasciatum). According to A Guide to Common Marine Fishes of Singapore, this fish can secrete a toxic mucus when harassed!


At the edge of the seagrass meadow, I was really happy to find this Dragonfish Sea Cucumber (Stichopus horrens). I had been scanning among the seagrass rather carefully, hoping to find it! And so why was I trying to find it? Because it had been quite a while since I last saw what I call the "Big Five Sea Cucumbers of Semakau". And today, finally, we saw all five of them - Synaptid, Sandfish, Stonefish, Ocellated and Dragonfish!


As we were crossing the seagrass meadow, I spotted this Noble Volute (Cymbiola nobilis) going after a clam! My first time seeing it actively hunting! As the volute touched the clam, the latter immediately extended its foot, pushed against the ground and flick itself out of the way. And somehow, the volute always knew which direction clam had moved to, and slowly glided towards it. It's unfortunate that I did not take a video of the whole process, as it was a really interesting scene! We had to go to rush for the boat though, and thus could not wait there to observe whether the volute would have a successful hunt.

All in all, it was a really great trip with a group of enthusiastic participants and lots of things to see!