Project Semakau Survey on 22 Jan 2011

We are back on Semakau again to survey the intertidal life on the island under Project Semakau! There were lots of sandflies and mosquitoes this time round - not sure if it's due to the large pools of water in the forest due to the monsoon rain. Fortunately, weather was fine though there were lots of dark clouds before we started the survey.

For this survey, I did a zone on my own.


Right at the start of the zone, I saw an Api-api Jambu (Avicennia marina) tree growing on the rocks! This mangrove plant is critically endangered in Singapore, though there's a good population on Semakau.


At the rocky area, I also found 2 Dolphin Snails (Angaria delphinus). These snails can sometimes be seen on some of our rocky shores.


There was also a Burnt Murex (Chicoreus brunneus). This snail feeds on clams by secreting an acid to soften the shell before creating a hole to access the meat using a tongue-like structure called a radula.


There were plenty of small little hermit crabs which I had no idea what species they were.


Tonight was a snaky night, as we saw quite a few Dog-faced Water Snakes (Cerberus rynchops). These snakes feed on fishes, and got their common name from the fact that the side profile of their heads resemble dog heads (with some imagination).


Moving on to the sandy shore, I found a Galloping Sand Star (Stellaster equestris) again!


And this was also the first time I saw an live snail at Semakau! Forgot the species name, so guess will have to check with the expert again in office :P


I also found a Marginate Conch (Strombus marginatus) which I have not seen on Semakau for quite some time. Somehow this snail appear to be seasonally abundant. Used to find quite a number of them on our northern shores and Semakau for a while, but hardly see them these days.


I saw a littel black object moving around among the rubble, and found that it was a Sponge Crab (Cryptodromia sp.)! This species often carries small pieces of sponge or ascidian to camouflage it.


The first slug of the day - Bohol's Nudibranch (Discodoris boholiensis)! Saw 2 of them on this trip.


There was also a huge Mangrove Horseshoe Crab (Carcinoscorpius rotundicauda), unlike the usual smaller ones we had been regularly seeing. There are 2 species of horseshoe crabs in local waters. To differentiate them, run your finger gently over the top of the tail. If it feels serrated and spiky, it's the coastal horseshoe crab. If it feels smooth, then it's the mangrove species.


There were also a few of these huge Synaptid Sea Cucumbers (Opheodesoma sp.) among the seagrass. Each was more than a metre long!


Wai Kit and Edmund found this very pretty Forskal's Sidegill Slug (Pleurobranchus forskalii).


The Denison's Nudibranch (Dendrodoris denisoni) appeared to be in season, and we saw quite a few of them.


Here's another one. You can see that the appearance of this nudibranch varies quite a bit.


This Striped Ribbon Worms (Baseodiscus quinquelineatus) was spotted among the seagrass too.


And less than a metre away was this juvenile Knobbly Sea Star (Protoreaster nodosus)! Semakau is one of the few places in Singapore where you can find good population of juvenile Knobbly Sea Stars - a good indication that they are reproducing well on this island!


And also within a metre of the ribbon worm was this Pseudobiceros uniarborensis flatworm. Along the way, I spotted many of them among the seagrass!


The other groups found a few brittle stars too!


Here's a closer look of the central disc.


And here's the underside, with lots of tiny tube feet! Hopefully the brittle star expert from Japan will be able to tell us the species when he's here after Chinese New Year.


And I spotted this little Red Shrimp (Processa sp.) among the seagrass. Sammy the shrimp expert will certainly be happy to see this!

Glad that it was again a great day with nice sightings!