Sunday, August 29, 2010

Semakau Walk on 28 Aug 2010

I had been sick for the past few days, and thus originally was thinking of giving this trip a miss. However, the fever finally stabilised by Friday afternoon, and I decided to go ahead with it. LK still did the main coordination work though, while I helped out with the hunting-seeking at the beginning, before heading out in search of shrimps for our shrimp workshop later in the afternoon.

I did not take many photos for this trip, so the organisms highlighted here were just some of the many things we saw that day.

Dragonfish Sea Cucumbers (Stichopus horrens) were really abundant today. I easily saw at least 10 of them even before I crossed the seagrass meadow. Some of them were really well-camouflaged among the sponges and silt-covered rocks.

I found this Cushion Star (Culcita novaeguineae) in the seagrass meadow. In fact, the other hunter-seekers found 2 more Cushion Stars later during the trip. This sea star got its common name from its cushion-like appearance, but it is certainly not soft and cuddly like a cushion. It feeds on corals.

The Sandfish Sea Cucumbers (Holothuria scabra) usually burrow in the sand, though on Semakau they are often seen on the surface as well.

LK spotted a net in the seagrass meadow with many dead animals. Unfortunately, Semakau is still not a protected area, and hence we often have fishermen coming here to set up nets and traps. This fish didn't look familiar, and I decided to flip it over to a better look.

It turned out to be a Remora (Echeneis sp.)! While I had seen remoras while diving in other countries, this was my first time seeing it in Singapore! This fish has a sucker plate on its head, which it uses to attach itself to bigger animals like sharks, rays or whales. The presence of this rather big remora (more than 30cm long) means there must be animals big enough for it to attach itself to! The relationship with the remora and its host is said to one of commensalism - meaning one party benefits while the other doesn't gain or lose much. The remora hence gets a free ride, and some species are said to feed on the leftovers food of the host, or even the host's feces.

There were many Giant Carpet Anemones (Stichodactyla gigantea) among the seagrasses, and this one has a small little anemonefish in it.

Most of the Sand-sifting Sea Stars (Archaster typicus) were paired up, performing pseudocopulation. The one on top is the male. They usually pair up up to 2 months before releasing their sperms and eggs into the surrounding water when tide is high.

Helen found 2 Noble Volutes (Cymbiola nobilis), and this was the smaller one she found. This huge snail feeds on smaller snails and clams by holding them in its muscular foot to try suffocate them.

The tide was rather high and hence we did not managed to go too far out to the reef area or even the outer edge of the coral rubble area. At the edge of the water, I found was this Stonefish Sea Cucumber (Actinopyga lecanora), looking just like a piece of well-eroded stone among the rocks in a tidal pool.

While heading back in the seagrass meadow, I found this Gafrarium pectinatum, a species of Venus Clam (Family Veneridae). Was quite glad to find this as while a few of the other volunteers and colleagues have seen this on Semakau, this was my first time seeing this species here. Unlike the similar-looking species, Gafrarium tumidum, which is rather common on Semakau, Gafrarium pectinatum appeared to be less commonly seen.

The walk soon ended, and I was really glad that the weather was perfect - cloudy, windy and not too hot, certainly a nice closure for our last Semakau walk of the year!

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