28 February 2015

Thousands of dead fishes at Pasir Ris

Thousand of dead fishes washed up at Pasir Ris beach today. Sean Yap also shared photos of dead fishes found on the same stretch of western Pasir Ris that I surveyed. He also blogged about it.
What is causing this mass fish death? Is it harmful to humans?

There was a line of dead fishes along the area I surveyed. Some had a thinner line.
In the part of the shore outside Pasir Ris Park proper, there was a bigger build up of dead fishes. But even here, the cleaners were trying hard to clear up the fishes. I also met Dickson Ng who was cycling in the area and went down to the shore. I asked for his help to go down the entire length of Pasir Ris Park to see how widespread the dead fishes are. He said it extended from the "west most end of the park to the outlet of sungei api api". Thank you Dickson!
Another look at the fishes that washed up here.
Here's video clips of the dead fishes here

They all seem to be the same kind and the same size. Are they wild fishes or fingerlings of farm fishes?
Fish A
There were many of these small fishes along the rest of the shore. Are they wild fishes or fingerlings of farm fishes?
Fish B
Here's some of the fishes that I saw. Some were very huge.
Fish C: Eeltail catfish, wild.
There were many of these eels.
Fish D: Eel, wild.
This fish is a surface dweller. And yet it got caught in the mass death. Does it mean that the problem really isn't low oxygen levels in the water? And that the fishes were killed by toxins from a Harmful Algal Bloom (HAB)?
Fish E: Halfbeak, wild.
This large solefish is a bottom dweller.
Fish F: Solefish, wild.
Here's more fishes that I can't be sure of their identity. Are they wild fishes or farm fishes?
Fish G

Fish H
There were also many dead cuttlefish and squids, some of them were very large.
Many of the fishes were bloated with their guts hanging out. I'm not sure what this tells us about the cause of death?
I chatted with this small team of hardworking cleaners who had been mobilised to clear the fishes on the waterline. They had already cleared the high tide line. It was clearly a fruitless effort because dead fishes just kept washing up after they cleaned. In the end, they told me they had no choice but to wait until after the high tide turned and to clear the high tide line.
In the area outside the Park and which is thus not cleaned, the old high tide line is still there. There were many crispy dead fishes here, probably washed up with the high tide last night or the day before.
Another large dead crispy fish on the old high tide line.
In this area, there are a series of pipes that appear to be either sucking in water or discharging water to the sea. Does this sort of activity affect water quality and thus make such mass fish deaths worse? I blogged about this issue some time ago.
In some parts of the beach, lots of fishes are gathered by the currents.
Some people on the beach are curious about the dead fishes. I advised the mum to keep her child out of the water.
The area I surveyed was about 800m near Pasir Ris Carpark E (yellow line).

More sightings of dead fishes in the same area on Sean Yap's blog.

Update 28 Feb: I just heard from a volunteer conducting a kayaking lesson today at Pasir Ris who shared: "When I was in the water kayaking the temperature felt slightly higher than normal. It was warm, which was a little unusual as we would usually feel colder when we soak in the water. There were also many catfishes swimming in the water, near the surface. (Possibly breathing whatever oxygen is diffused?) There were a few eels as well. Around 4.30pm, there was one row of fishes along the water line. It felt like a shiny line of tragedy."

Update 1 Mar: There was mass deaths at the fish farms, according to media articles.

Recent posts about dead fishes at Pasir Ris and elsewhere

What is killing the fishes at Pasir Ris?

Around the same time last year, there were mass fish deaths at the Eastern fish farms located in the waters between Pasir Ris and Pulau Ubin. Conditions now are rather similar to last year: cloudless dry weather leading to higher water temperatures in the narrow Johor Straits.

Higher water temperatures allow tiny organisms in the water to reproduce more rapidly. These include algae which consequently 'bloom' or rapidly increase in numbers. Like other living organisms, these absorb oxygen. The population explosion thus leads to a rapid reduction in dissolved oxygen in the water.

As populations of oxygen-sucking organisms explode, they create 'dead zones' in the water lacking oxygen. These zones kill immobile or slow-moving animals. Animals that swim into such a zone can succumb quickly and die too.

Is it important to find out exactly what are killing the fishes at Pasir Ris?

Yes, if we care about the health of people who eat the fish raised or caught in these waters, or who use the shores.

Besides killing marine life by reducing oxygen levels, some kinds of algal blooms can be dangerous to humans too. These are often referred to as 'red tides' (although they are not always red or caused by the tide) and more properly called Harmful Algal Blooms (HAB). Such a bloom can be dangerous because the tiny algae produce toxins. Filter-feeding animals such as clams concentrate these toxins. The toxins do not harm the clams, but can be fatal to humans and other animals such as otters that eat the clams. Crabs and other marine creatures can also concentrate these toxins. The toxins are not destroyed by cooking.

People should also be advised to avoid going to the areas affected by Harmful Algal Blooms (HAB). For some kinds of toxins produced by such a Bloom, anecdotal evidence suggests that people who swim or inhale such toxins dispersed in the air may experience irritation of the eyes, nose, and throat, as well as coughing, wheezing, and shortness of breath. Additional evidence suggests that people with existing respiratory illness, such as asthma, may experience these symptoms more severely. I have been told by scientists that the symptoms are similar to those of the flu so many people may not realise they are suffering from exposure to Harmful Algal Blooms (HAB). More about red tides here.

Are the recent fish deaths an early indications of a Harmful Algal Bloom (HAB)? If there is a Harmful Algal Bloom at Pasir Ris then fishes and marine life raised in these waters should not be sold to the public, and there should be public alerts to warn everyone not to eat fishes or marine life raised or caught in the waters.

More about what likely caused last year's mass fish deaths which includes some suggestions already made last year about avoiding a similar situation from recurring.

Mass fish deaths also occurred at the Western fish farms located near Sungei Buloh and Lim Chu Kang in October last year.

What can we do to improve water quality at Pasir Ris?

Cleanliness surely is a key element of water quality and healthy ecosystems. While there are many variables that we may not be able to control, there are some that we can. If AVA can provide trash collection service during a mass fish death event, why can't they provide a trash collection service regularly? Why can't fish farmers be provided daily door-to-door trash collection like every other household, business and ship parked in Singapore port? More about this issue here. Today, I continue to see trash on the shore that clearly come from the fish farms.

You CAN make a difference: Dead Fish Alert!

Please help me monitor dead fishes washing up on the Johor Straits. Please let me know if you see large numbers (more than 10) especially of large dead fishes (more than 20cm long) washing up on the northern shores such as Pulau Ubin, Lim Chu Kang, Sungei Buloh, Kranji, Sembawang, Punggol, Pasir Ris, Changi.

Thank you!

Past incidents of mass fish farm deaths on our shores

Eastern fish farms mass fish deaths

Western fish farm mass fish deaths


  1. A & B look like glass perchlets (Ambassis sp.), probably a mixture of the 2 species found in Singapore, the Kops' Glass Perchlet and Telkara Glass Perchlet, with some assorted smaller fishes - all wild, but also possibly harvested as fish food.

    C is a Sea Catfish (F. Ariidae)

    D is a Moray Eel (F. Muraenidae), F is a Tongue Sole (F. Cynoglossidae), if you need more specific IDs.

    G is a Barramundi, H is a Grouper - these are the only ones that might be farmed in this series of photos, I believe the rest are all wild.

    This is most worrying.

  2. the section about what we can do sounds a bit iffy given that the probable cause of the fish kill incident could be due to algal bloom or deoxygenation.

  3. Thanks Bai for the comment. I think it's good to find out the extent of fish deaths along the Johor Straits, so the authorities and scientists can investigate. If people can share what they have seen, I think this is help us work towards this. Why do you think this is iffy?

  4. very sad to see so many dead fishes. I myself am a fish lover. even catch clams at sungei pandan swamp. Thk God here is not affected.

  5. Thank you Ricky, for sharing that all is ok at Sungei Pandan!

  6. chemical and refineries at JB side can be one of the source of suspect as well. Many refineries uses seawater as a cooling medium to cool down process and discharge back into the sea.

  7. Fish bombing in offshore islands?

  8. Yee-chan, in Singapore I believe there is no fish bombing in any of our waters. This kind of harvesting method is more common in reefs elsewhere in Asia.

    1. I'm not implying fish bombing is employed in Singapore waters. Do you know where are the closest reefs to Singapore?

  9. Such a sad sight, Ria... hope there's more we can do...



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