wild shores of singapore: Happy National Day from Big Sisters Island!

On the last predawn surveys of the year, we celebrate National Day by checking up on Big Sisters Island, with permission from NParks. A night survey means more sightings of fish and other animals that hide during the day. Our last night survey here was in Sep 2020.

National Day(ish) at Big Sisters Island, Aug 2025

With a full team, we find healthy corals (except for some Boulder pore corals). Two Cushion stars were seen, and a large shark! As well as the usual colourful crabs, 'Nemos' and reef fishes, nudibranchs, octopuses and other familiar favourites.

As usual, we see more fishes during a night survey. I saw fishes usually seen only on good reefs like the Anchor tuskfish, well camouflaged despite its pretty colours, and Eight-banded butterflyfish as well as the Bengal sergeant. There were also the usual filefishes and other small fishes. I didn't see any Silversides which are usually so common on our reefs at night, jumping about and messing up my photos. The rest of the team saw Nemos and other colourful fishes too. I will update with their sightings later.

I came across the Cushion star that we heard was seen here. And I found the Fluted giant clam by tripping over her - she seems to have grown. I also saw the usual colourful crabs found on our reefs. There were also many rather large Purple climber crabs on the seawall as well as swarms of Sea slaters. The rest of the team saw even more, including a second Cushion star, shark, lots of octopuses and many nudibranchs.

In the Big Lagoon, the coral situation seems similar to our last survey here in Feb 2025. It's nice to survey corals at night, as many have their polyps expanded and they often have beautiful colours. I saw the usual variety of hard corals. Mostly boulder shaped ones, but also many plate corals and some less common kinds. There were also many small colonies on the artificial seawall. Most of those I saw were alright although many colonies had large dead portions. I couldn't find any Anchor corals. The team saw special corals outside the seawalls, I will update with their finds later.

Although I didn't see any corals that were bleaching, and most were okay, about 10% of the large Boulder pore corals that I saw in the Big Lagoon had a narrow ring or small patches of dying tissues (white or blue and smells of rotting tissue). I did not observe this on our last survey here in Feb 2025.

In the Big Lagoon, I also many leathery soft corals, with small ones in the middle of the lagoon of various kinds. Larger ones nearer the seawall. I didn't see any that were bleaching but some of the larger Omelette leathery soft corals were covered in sediments, not sure if this means they are not well.

It was a little alarming to see some patches of very pale Button zoanthids, although the Sea mat zoanthids seemed alright. Other than this, the situation for other cnidarions seems similar to our last survey here in Feb 2025, the Giant carpet anemones remain abundant. I also saw many Corallimorphs and only one Asparagus flowery soft coral. They all seemed fine. This situation is similar to our last survey here in Feb 2024, which was before the global mass coral bleaching event.

There are some patches of sandy shores in the Big Lagoon. There, I saw a snail that I've not seen before. There were a few Oval moon snails. Also some signs of Acorn worms, and on the higher shore: Sand bubbler crabs and Ghost crab burrows. I didn't see any marine life in the Small Lagoon which has been modified so water is retained even at low tide. In the past, I used to see Common sea stars here.

There seems to be a bloom of cyanobacteria on much of the shore in the Big Lagoon. With dense growths in the mid-water area, and more patchy growths towards the seawall. I didn't see any seagrasses today.

There is a narrow natural rocky shore facing Small Sisters Island and the boardwalk on Big Sisters Island. With a natural cliff and natural pebbly shore.

I saw the usual snails and other marine life commonly seen on our natural rocky shores. Nerite snails and their egg capsules. Drill snails, Ceriths, Dove snails. Grazing on 'meadows' of fine seaweed in shady areas were little onch slugs. In sheltered crevices, little Volcano barnacles. There were clusters of Huddling hermit crabs.

A small natural coastal forest grows on this natural rocky shore. This morning, the air was full of the fragrance of flowering Penaga Laut. I was delighted to see two Delek Air trees, one was quite large. Both were fruiting, no flowers seen. There was also a small Sea teak it was producing male cones. The Seak teak is a conifer. That is, it produces seeds but no flowers. All these plants are Critically Endangered in Singapore. Since the enhancement works, you can now walk the 230m Coastal trail up the hillside where the forest grows and ending at a two-storey high hilltop view deck - the highest point of the island.

Most of the shores on both Big and Small Sisters' Islands were reclaimed: seawalls were built on the reef edge and the reef flat buried. The original islands were much tinier. Most of Big Sister's Island is ringed by artificial seawalls, which create two swimming lagoons. Since the reclamation, living corals have returned in the big lagoon of Big Sisters Island. The latest Google Earth images show the newly constructed boardwalk!

The two Sisters Islands were designated as a Marine Park in 2014. Big Sisters Island was closed in 2021 for enhancement works and reopened in 2024 with a new boardwalk and other facilities. Like many parks in Singapore, you can visit Big Sisters Island any day from 7am to 7pm. You don't need a guide or a permit to visit during these times. Our predawn survey today was done with permission from NParks. Small Sisters Islands is not open to the public and reserved for research work. More about the Sisters' Islands Marine Park on the blog and facebook page. More on the NParks website about what you can see and do at our Sisters Islands Marine Park.