Semakau Over Last Weekend

Went to Semakau over the weekend for a Project Semakau survey and also a guided walk for secondary school students. Once again, I was the coordinator for both trips. For the guided walk, NEA had only provided one bus for the trip and we had like 80 participants, and thus I had to stay with the participants to coordinate the landfill tour instead of running off to help with hunting-seeking. Fortunately, I still managed to find a few interesting stuff for the participants even though I went to the intertidal area rather late :P

Here are some of the things we saw over the weekend.


There were several Magnificent Anemones (Heteractis magnifica) near the reef edge. I did not find any anemonefish in them though.


Semakau has many species of hard corals, and the above is a Galaxy Coral (Galaxea sp.). The colony has lots of small tentacles with white tips, which resemble stars of the galaxy, and hence the name.


The Upside-down Jellyfish (Cassiopea sp.) was in season, and we saw a number of them on both trips.


Moving on to the echinoderms, we saw quite a number of Sandfish Sea Cucumbers (Holothuria scabra) despite the heat.


There were a few Dragonfish Sea Cucumbers (Stichopus horrens) too.


The Stonefish Sea Cucumber (Actinopyga lecanora) was not as numerous though. I only saw 2 of them.


Semakau has a huge population of Sand-sifting Sea Stars (Archaster typicus), that blend in really well with the surrounding sand.


It was really a day for Cushion Stars (Culcita novaeguineae). This was the smallest one we saw that day, only about 6-7cm wide.


This one was slightly bigger, about 8cm wide, I would think.


This one was regularly spotted around the same area, and it had certainly grown! The first time I saw it, it was only about 5cm wide, and now it's probably about 10cm wide.


And we also found this huge Cushion Star which we saw every now and then on Semakau. It is definitely more than 20cm wide. Some of the groups saw yet another huge one later, one which I last saw in 2008!


Semakau probably has hundreds of Knobbly Sea Stars (Protoreaster nodosus).


This was also the first time I saw this black flatworm with orange outline on Semakau. Not sure of the ID though.


There were also a number of molluscs around. The above shows the underside of a Spider Conch (Lambis lambis), which got its name from the long spines which supposedly resemble spider legs to some people.


Another pretty snail we saw was this Noble Volute (Cymbiola nobilis). This snail hunts other snails and clams to feed on.


One of the guides found this Starry Bornella (Bornella stellifer), a nudibranch which I had not seen on Semakau for a few years!


Even more colourful was this Varicose Phyllid Nudibranch (Phyllidia varicosa). This slug can secrete a whitish toxic substance into the surrounding water when it's stressed. Was rather excited to find this since I had not seen it for quite a while.


I also found some nudibranch egg ribbons among the seagrass.


Our good old resident Fluted Giant Clam (Tridacna squamosa) was still at the same old spot.


I found this bivalve during the survey - my first time seeing it on Semakau. Have not checked with SK what it is, though it sure looked like some kind of mussel. Update: Have checked and it is a Brown Mussel (Modiolus philippinarum).


Another nice find of the day were a pair of Tigertail Seahorse (Hippocampus comes). The above is a female.


And this is the male Tigertail Seahorse. Looks like it's pregnant. Male seahorses have a brood pouch, which the females will deposit their eggs inside, and the former will then fertilise and protect the eggs until they hatch.

It was certainly 2 very hot days on Semakau, but certainly 2 very fulfilling days for me with many great sightings! :)