Sunday, June 15, 2014

Coral rubble survey at Pulau Sekudu

With permissions from National Parks Board, we were back at Pulau Sekudu to survey the coral rubble on a lower spring tide. I ended this trip with mixed feelings with both exciting and not-so-happy finds.

What's exciting would be my first time seeing the boxfish! Many thanks to Marcus for spotting it! Don't you think it is very cute? :)

This fish is also a clear reminder not to put keep all our emotions in the box, for us to also think out of the box! We named it Boxie and were reminded of boxing name. Of course, we were cautious not to be boxed by this fish. x_x

This boxfish is likely to be the Shortnosed boxfish (Rhynchostracion nasus) whose distinguishing features are a small bump on the snout above the upper lip, and a ridge along the middle of the back. It was swimming up and down for quite some time before it decided to take a break.

The boxfish has a strong and hard body shell. This species is likely to be able to secrete a powerful toxin on the skin (called ostracitoxin). This toxin is poisonous to other fishes and can even kill the boxfish itself if it is confined in an aquarium. Thus they are not recommended for aquariums.

Another special fish which Ria found at the coral rubble would be this brightly coloured Estuarine seahorse (Hippocampus kuda).

It was first found clinging onto the yellow Sea fans or Gorgonians (Order Gorgonacea) though it swam away shortly after we took a look at it.

There are hard corals on the coral rubble such as several colonies of the Pore hard coral (Porites sp.) which we also saw at the coral rubble of Chek Jawa which is only separated by a stone's throw away across the channel.

I also came across one colony of the green Sandpaper coral (Psammocora sp.).

What was sad about the coral rubble was the decimation of sponges that used to cover many rocks of the reef. This was also what we observed at Chek Jawa the day before. It's quite worrying as it is not a localised phenomenon. We wonder what causes this situation. 

The two main types of sponges that still can be found would be the Yellow bumpy sponges and the Chocolate sponge. The rocks were also mostly coated in Melted chocolate sponge.

As for the other types of sponges, they are seldom seen and those what exist are very small in size. It's strange that the Purple branching sponges (Callyspongia sp.) which can be found in large numbers on mainland shores such as Changi are not even able to thrive at Sekudu or Chek Jawa. 

The sea slugs mainly feed on sponges such as this Black-margined nudibranch (Glossodoris atromarginata) that was seen feeding on the black sponge. Having less sponge means less food and also less slugs.

Similar to the seagrass areas, the White sea urchins (Salmacis sp.) are found in great numbers on the coral rubble of Sekudu.

There were some sea fans though not as abundant as those in Changi or East Coast.

As for Feather stars (Order Comatulida), I only saw one at the coral rubble instead of the few that we usually would find in the past.

Also sadly missing would be the Biscuit stars (Goniodiscaster scaber) that used to be found in higher numbers in the past. I only saw one at the rubble area today. It's puzzling that I see a lot more just a stone's throw away at Chek Jawa.

I also took the time to check the huge boulders and was pleasantly surprised to find both the Onyx cowries (Cypraea onyx) and also the Scaly sea star (Nepanthia sp.)!

Here's a closer look at the Scaly sea star which I was trying to find on my previous two trips at Sekudu and Chek Jawa. Glad to see it today!

The Knobbly sea stars (Protoreaster nodosus) are still alright and since today's trip ended after sunrise, it was a great opportunity to take a photo of the scenic background with the sea star in front. :)

I saw a good number of 8 knobblies! The one on the bottom right was found right in the middle of the lagoon by Ivan. That's unexpected as they are usually found closer to the edge.

Chay Hoon found another exciting find! It is probably the largest Oval heart urchin that we have seen. It is still alive and is as nearly as huge as the size of our palms. They got their name because they have a heart-shaped body.

Here's the underside of the heart urchin. A heart urchin's mouth is on one end of the oval-shaped body. Its anus is on the opposite end of the body

She also found this special Arrow-head spider crab that has a small piece of algae attached to it! We have never seen this before!

More beautiful sea slugs were found by Chay Hoon and Ria! The first one is the Aeolid nudibranch (Cratena sp.) which I've also seen at Chek Jawa yesterday. It's really tiny!

Another tiny slug which only Chay Hoon can find would be this Cerberilla sp. slug. Can you spot the eye spot on this slug?

Ria found three of these Aeolid nudibranch (Flabellina sp.) on the hydroids!

More slugs found by Ria would be this Chromodoris nudibranch (Chromodoris tumulifera) that looks like a cow with its dots on the body.

Another pretty slug would be this Hypselodoris nudibranch (Hypselodoris sp.) that is sometimes also seen at other northern shores such as Changi.

I took some landscape shots and like this one with the two types of birds- the ones on the shore and the bigger one flying!

There were many traces of dugong feeding trails and they serve as a reminder that these majestic and huge mammals are still thriving on our waters though they are very seldom sighted. The Naked Hermit Crabs once saw a living one just off the waters of Chek Jawa!

Unfortunately, we came across fish traps and drift nets on the shore despite the fact that this island is out of bounds to the public. Here's a photo of the length of a drift net with Ivan in the photo as a scale.

We contemplated whether to remove it but decided not as it was overgrown with algae and other encrusting marine life. It has become a habitat by its own and shouldn't pose much of a threat. Nevertheless, we removed a newer one on Friday morning as it may cause harm to marine life big and small.

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