12 May 2013

Giant surprise at Sisters Island

What a surprise to see this rather large  Fluted giant clam (Tridacna squamosa) on Big Sisters Island!
We also spot seahorses and other intriguing marine life, on a wonderful day out on our shores.


We survey this island very regularly. How we could have missed this Giant clam in all these years? Together with the five smaller Fluted giant clams we saw for the first time yesterday at Pulau Hantu. What is going on with this 'sudden emergence' of giant clams? Mei Lin aka Giant Clam Girl shares her thoughts about this puzzle on her blog. Regardless, we are quite encouraged by these finds!

All the Sargassum seaweed (Sargassum sp.) has disappeared from the shore. So of course, we can find the seahorses here more easily, unlike during our last trip here with Tse-Lynn! This looks like a pregnant papa seahorse. I'm not sure why he has a big pink-edged hole on his tummy. Did he just 'give birth'? There was another seahorse nearby. Both of them were covered with a fine coating of furry growths, but they had banded tails so they are probably Tiger-tail seahorses (Hippocampus comes). I couldn't find any other seahorses today.
As we were distracted by the seahorses, Mei Lin spotted this super tiny frogfish (Lophiocharon trisignatus) nearby! Pei Yan also spotted a Burrowing snake eel (Pisodonophis crancrivorous) eating an octopus!
It takes some practice to spot our marine life. The shell of the Spider conch (Lambis lambis), for example, is encrusted on the upper side so it is hard to spot among the equally encrusted rubble.
On the underside, the snail is pearly and colourful! Unlike most other snails that creep slowly about, Conch snails 'hop'. The snail has a knife-like operculum which is used to stick into the ground to lurch about.
Although I didn't see any obviously bleaching hard corals, I came across some that seemed ill. I remember similar sightings last year May 2012 around the same time. This Pore boulder coral seems to be suffering some sort of disease on the upper part of the colony.
Some of the large Pore corals (Porites sp.) had pale upper rims and bluish sections. I saw a colony of Carnation corals (Pectinia sp.) with fluffy green algae growing on the upper parts of the colony.
Sadly, the Carnation corals (Pectinia sp.) on the right seems to be dying. Although the Ridged plate coral (Merulina sp.) on the left seems to be doing fine.
This is what the same coral colonies looked like about a year ago in Jan 2012.
Some of the Circular mushroom corals (Family Fungiidae) were bleaching or bright pink with dead portions. But most seemed normal.
The Brain anchor coral (Euphyllia ancora) seems fine and I saw several Crinkled sandpaper coral (Psammocora sp.) which didn't look obviously bleached although some were pale. I didn't see any Cauliflower corals (Pocillopora sp.). These species were among the first to bleach during the global coral bleaching event of 2010.
Some of the Brain corals (Family Mussidae) were rather pale.
Most of the corals I saw, though, seemed normal: mostly Pore corals (Porites sp.) and  Favid corals (Family Faviidae). As well as other common kinds of hard corals.
I've started to pay closer attention to hard corals and realise I don't quite know what this one is.
The Leathery soft corals (Family Alcyoniidae) I saw seemed alright. I didn't come across any flowery soft corals.
There are all kinds of sea anemones on this shore and those I saw looked alright today: Giant carpet anemones (Stichodactyla gigantea), Frilly sea anemones (Phymanthus sp.), what seems to be a Bubble tip anemone (Entacmea quadricolor), many Peachia anemones (Peachia sp.), Haddon's carpet anemone (Stichodactyla haddoni) and clusters of the mysterious white tipped anemone-like creature. While Marcus saw signs of 'Nemos' some of the large sea anemones, the rest of  us missed these. This shore is somewhat heavily impacted by fishing. We even once came across two driftnets laid in the lagoon in Oct 2011.
There were many Glossodoris atromarginata and I saw one Jorunna funebris as well as several Ornate leaf slugs (Elysia ornata) among the seagrasses. The rest of the team spotted the Fugly nudibranch (Actinocyclus sp.) and other kinds of slugs.
There were two of these Long-spined black sea urchins (Diadema sp.), rather small ones. I haven't seen them for quite a while.
This fanworm looks different from the usual Fan worms (Family Sabellidae) that I see. Hopefully, in the upcoming Southern Expedition, we can take a closer look at the biodiversity in our Southern shores and learn more about them.
I was surprised to see so much seagrasses inside the smaller lagoon on the island.
There is a small clump of Tape seagrass (Enhalus acoroides) in the lagoon and tiny-bladed Spoon seagrasses (Halophila ovalis) have densely covered about one third of the sandy lagoon. I also saw a small clump of Sickle seagrass (Thalassia hemprichii) outside the seawall, and there remains a sprinkling of Spoon seagrasses in the big lagoon.
There are also still many Common sea stars (Archaster typicus) on in this lagoon. I also saw a super tiny Common sea star among them.
I almost overlooked the Land hermit crab (Coenobita sp.) that had curled up inside a Fig snail shell among the similarly shaped Sea almond fruits (Terminalia catappa) on the grass. The shell is way too small for the animal. This is why we should NOT remove empty shells from the sea shore. They are potential homes for hermit crabs who may die if they cannot find a shell to protect their soft backsides.
Oh dear, a big tree had fallen on the island. It had been cleared up so the path was passable. The roots are rather shallow (our red cooler box in the photo for scale). This is why we need to be careful on the islands during bad weather with strong winds.
The visibility was great today and we could see right to the reefs on the edge of the shore as fishermen started setting up their rods on the pontoon.
We saw this man on Little Sisters Island fishing on the reef edge. He only started to moved back to the seawall as the tide rose. Fortunately, he seemed to make it back alright.
There are fierce wild monkeys on both Big Sisters and Little Sisters Islands. They emerged from the forested area and rushed towards us as we started to take plastic bags out to put our wet things in. These monkeys already associate humans with food. As Marcus and Rene took photos of them, they fearlessly kept rushing up towards us.
Clearly, we should not mess around with these well-endowed animals.
We started our trip well before dawn, with the lights of the business district on the mainland lighting up the sky.
And enjoyed a spectacular sunrise over St. John's Island on the horizon!
It was a scorching morning and as the tide turned on beautiful Big Sisters Island.
A view of Singapore business district just 15 minutes away by fast boat, with Pulau Tekukor infront of it.
We will soon be back with a vengeance on the southern shores during the Southern Expedition which starts next week!

Posts by others on this trip
  • Mei Lin on her blog with more about the Giant clam and other interesting critters.
  • Marcus on facebook

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