21 July 2013

Predawn at Chek Jawa, after 10 years

It's been ten years since I surveyed the coral rubble area of Chek Jawa at night. It was nice to see that sponges seem to be coming back there.
The tide wasn't very low but we managed to see some familiar favourites as well as some new finds. Sadly, we also came across a driftnet laid across this richest part of Chek Jawa.


Although there were small clumps of a variety of sponges, the shore is not as 'spongey' as it used to be a long long time ago.
Rich coral rubble of Chek Jawa
Sponge garden at Chek Jawa in 2002
But the shore remains very starry! Kok Sheng found a baby Knobbly sea star (Protoreaster nodosus), Ivan found a pretty Cake sea star (Anthenea aspera and a large Eight-armed sand stars (Luidia maculata). There was also a Spiny sea star (Gymnanthenea laevis), as well as the usual sand stars (Astropecten sp.) and lots and lots of Biscuit stars (Goniodiscaster scaber).
Not too many different kinds of sea cucumbers, the Pink warty sea cucumbers (Cercodemas anceps) and Thorny sea cucumber (Colochirus quadrangularis) were not as abundant as at Changi. Ivan found a Beige sea cucumber. And I only saw one White sea urchin (Salmacis sp.). There were many Garlic bread sea cucumbers (Holothuria scabra) in the seagrass meadows near the rubbly area.
Among the seagrasses on the landward side of the Southern sand bar, there were lots of elongated sea cucumbers writhing above ground. We counted more than 15 of them in a small area. I've never come across this before. Are they Ball sea cucumbers (Phyllophorus sp.) that have emerged from their usual buried position, perhaps to mate with the incoming tide? Or are they some other kind of sea cucumber? So much more to learn about our shores.
I saw two large octopuses that look like the kind that we see on reefs. The rest of the team also saw a large squid. And there were many Noble volutes (Cymbiola nobilis).
I came across three Chromodoris lineolata nudibranchs, including this pair that look like they are about to make new nudis. Although more commonly seen on our Southern shores, we have spotted these too on our Northern shores including other parts of Pulau Ubin and on Pulau Sekudu. Chay Hoon, of course, also spots all kinds of other nudis and slugs (some are so tiny I have no idea how she spots them in the dark!).
There were many crabs on the shores. At night the Leaf porter crab (Family Dorripidae) sits above the leaf to hide from predators in the water, but will flip over when it notices my torch. There was also a Maroon stone crab (Menippe rumphii) as well as many different kinds of Swimming crabs (Family Portunidae).
Ivan found this special crab that carries coral rubble around. Marcus Ng (who couldn't be with us on this trip), had earlier posted lots of info and a great video clip of the crab (Actumnus setifer) using its rubbly shelter.
Tiny and small shrimps of all kinds were busy on the shore including: Prawns (Family Penaeidae), snapping shrimps (Family Alpheidae) and various kinds of tiny shrimps.
One of the reasons for doing a predawn trip is to observe shy animals such as fishes. I saw what looks like a large hidden wrasse (Family Labridae), several small Kite butterflyfish (Parachaetodon ocellatus), Rabbitfishes (Family Siganidae), toadfish (Family Batrachoididae). The rest of the team also saw several different kinds of sting rays and other fishes.
We had a look at the legs of the boardwalk while waiting for the tide to go down. Among the barnacles is a kind of fly that crawled around. Did it lay eggs from which these tiny yellow maggots emerged? The maggots were vigorously looping around, and one tiny crab seemed to be eating a maggot. I've noticed insects in the barnacle zone on Changi as well as at the East Coast.
There were a few clumps of soft corals, including a tiny patch of Fine feathery soft corals (Briareum sp.), Spiky flowery soft corals (Stereonephthya sp.). At the beacon, there was one large Pink flowery soft coral (Family Nephtheidae). The water was too high to explore the beacon area properly. There were also some small Flowery sea pens (Family Veritillidae), Spiky sea pens (Pteroides sp.) and in the seagrassy areas, some sea pencils and cerianthids (Order Ceriantharia).
There was an explosion of Swimming anemones (Boloceroides mcmurrichi) all over the seagrass meadows with a range of these anemones from tiny to the usual adult size. Another abundant anemone were Posy anemones. Of course, there were lots of Haddon's carpet anemones (Stichodactyla haddoni) all looking healthy. I also saw one small Tiny carpet anemone (Stichodactyla tapetum).
Then there were these tiny anemones dotting sponges on the coral rubble area. I have no idea what they are.
There were also many different kinds of ascidians on the coral rubble.
Fluffy fan worms (Family Sabellidae) are common among the rubble, as well as lively bristleworms roaming among the seagrasses.
Flatworms still abound here. I saw several Blue-lined flatworms (Pseudoceros sp.) and two pairs of Purple-spotted flatworms (Pseudoceros laigensis). Of course many tiny Blue spotted flatworm (cf Pseudoceros indicus).
We saw two of these large flatworms with fine lines. The Fine-lined flatworm has yet to be identified and is not often seen. In the past, I used to see them often at Chek Jawa so it's good to see that they are still there.
Alas, we came across a driftnet laid right across the rubble parallel to the water line from south to north. We could not find the other end before the tide came it, we suspect it is more than 200m long. It was laid on top of all kinds of marine life that might be damaged or uprooted when the net is removed.
The net had already uprooted this pretty sea fan.
Ivan tried to release as many of the live fishes as he could before the tide came in. More about this net on Project Driftnet.
This is not the first time we've seen nets on Chek Jawa recently. We saw abandoned nets in Apr 2013 and Jan 2013, some near signs of dugong feeding trails. We also saw a fisherman lay a very long driftnet inside the Chek Jawa lagoon in February 2013. The issue of driftnets on Chek Jawa (and elsewhere) is a painful one and does not have an easy or quick solution.

Ivan found this huge fish isopod stuck on a small fish that was entangled and dead on the fish net.
The Fern seagrass (Halophila spinulosa) were particularly lush in the area I surveyed. As at Changi, I noticed Beige sheet ascidians growing on Spoon seagrass (Halophila ovalis) (and only on Spoon seagrasses it seems). I also noticed that the Ribbon seagrasses were growing on the seaward side of the Southern sand bar too. There was also Needle seagrass (Halodule sp.).
There were also all kinds of colour seaweeds on the shore, but not overwhelming the seagrasses. Most of them grew in small clusters on the rubble.
As I went to wash up, a swish of wings overhead revealed an owl!
What's missing at Chek Jawa?

Compared our recent trips to nearby shores such as Changi and Pulau Sekudu, we didn't come across some expected animals. But this could be because we didn't go at a minus-zero tide. I didn't come across any Sea fans, Ball flowering soft corals (Dendronephthya sp.), no hard corals except for a tiny patch of Zebra corals (Oulastrea crispata) and no hydroids (Order Hydrozoa). There also didn't seem to be many Fan clams (Family Pinnidae) and Window-pane clams (Placuna sp.) compared to Changi. We didn't come across feather stars (Order Crinodea) or large brittle stars (Class Ophiuroidea). We hope to do another predawn survey of Chek Jawa this year to cover the areas that we missed due to the highish tide. Hopefully, we will find these 'missing animals' then.

Why did I restart the pre-dawn surveys at Chek Jawa?

We can't take Chek Jawa for granted. There are plans that may affect Chek Jawa in the not too distant future. These include plans to locate at Pengerang Johor, a petrochemical complex that was rejected in Taiwan for environmental and health reasons.
The 2030 landuse plan by the Ministry of National Development includes plans for a road link (black line) from the mainland jumping off at Punggol, crossing to Pulau Ubin through Chek Jawa to jump off to Pulau Tekong before circling back to the mainland on Changi East. Proposed reclamation (in yellow) will bury Pasir Ris shores, Pulau Sekudu and Chek Jawa as well as a large amount of shore at Changi Beach.
Click on images for larger view.
I feel it is thus important to update our understanding of what is going on in the field at these sites including Chek Jawa.

Thanks to NParks for permission and support to do these predawn low spring tide surveys of Chek Jawa. Thanks also to Chay Hoon for making all the transport arrangements. And the team for helping to cover as much ground as we can during the narrow low tide window. There are very very few people who not only can do such an awesome job but also turn up at 1am for the trip! Thank you.

Tomorrow, we will be surveying Pulau Sekudu which also lies within the Chek Jawa Wetlands area.

Posts by others on this trip
  • Chay Hoon on facebook with lots of slugs!
  • Kok Sheng with all kinds of sea stars, slugs and more. 
  • Pei Yan shares her first predawn trip to Chek Jawa 

1 comment:

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