25 February 2015

What is killing fishes at Pasir Ris?

I received this photo of more fishes dying at an eastern fish farm today.
Photo from Sea Angle Boatfishing on facebook.
 So I headed out in the afternoon to see if dead fishes were washing up at Pasir Ris Park beach.
Large dead fish floating up at Pasir Ris beach.
There was a huge dead barracuda, and a few other large dead fishes. I didn't see many dead farm fishes. Dead wild fishes were also reported over the last two days at Sembawang and Changi. The risks of fish deaths are rising in the weeks ahead as there will be no good spring tide to flush the waters around Pasir Ris and Pulau Ubin until April.

I checked out the western side of Pasir Ris today, the same stretch I checked three days ago on 22 Feb (Sat). Alas, today I came too late and the cleaner had already cleaned the high water tide line for the day. So I only checked the low water line of the most recent tide.
This huge dead barracuda was floating in the water.
Fish A: Barracuda, wild.
Fish B: Unknown, wild.
Fish C: Archerfish, wild.
Fish D: Pufferfish, wild.
Fish E: Unknown, wild.
Fish F: Green-spotted pufferfish, wild.
I also surveyed a stretch of beach wasn't cleaned yet. So I could check the high water tide line for today.
Here, I saw a few very crispy large dead fishes.
Fish G: Unknown.
Fish H: Unknown.
I also surveyed the western stretch of shoreline that is outside the Pasir Ris Park proper and thus is not cleaned at all. Here, I saw some really large dead fishes.
Fish I: Unknown.
Fish J: Toadfish, wild.
Fish K: Unknown, wild.
Fish L: Unknown.
Fish M: Green chromide, wild.
Fish N: Eel-tailed catfish, wild.
I also checked out the eastern side of Pasir Ris Park on Sunday 22 Feb and saw several dead wild fishes.
Fish O: Unknown.
Fish P: Eel-tail catfish, wild.
Fish Q: Unknown.
Fish R: Unknown.
Fish S: Snapper? wild.
Fish T: Unknown.
Fish U: Pompano, farmed.
Fish V; Spotted scat, wild.
Thanks also to those who responded to my facebook appeal to report sightings of dead fishes over the last two days. Benjamin Li reported on 25 Feb: "Casualties spotted at sembawang area. Photos not very clear but looks like pampano and tilapias." sharing Jeffery Tsen's photos on Sampan Trips.
Photos by Benjamin Li on facebook.
While Xu Weiting reported on 24 Feb: "Was near Changi Beach carpark 1 this morning and saw about 5-6 dead fishes on the coast. Most of the casualty fishes were non-farmed ones."
Photo by Xu Weiting on facebook.

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.

Today, in some parts of the shore, there were lots of broken off Spoon seagrass floating in the water. I noticed last week that large stretches of Spoon seagrass were bleaching on the eastern side of Pasir Ris. Is this a sign of elevated water temperatures?

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.

AVA finally collecting dead fishes from the farms?

Although it's heart-breaking to see the fish farmers' months of hard work floating up dead.
Photo from Sea Angle Boatfishing on facebook.
It is heartening that I didn't come across large numbers of dead farm fishes washing up on the shore today. Which I did during previous mass fish deaths. Hopefully this means AVA is providing a service to collect the dead fishes from the affected farmers?
Photo from Sea Angle Boatfishing on facebook.
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. Some tentative identifications:

    Fish B: Eel (not sure if moray or snake eel)
    Fish E, K: Juvenile Eeltail Catfish
    Fish G, H, Q, S: Snappers
    Fish I, L, O, T: Barramundi
    Fish R: Some sort of herring, possibly Kelee Shad (Hilsa kelee)

  2. Thanks for these important on-the-ground reports. Really sad to see the fish die and along with them the farmers' livelihoods... Any other suspects as to what's causing the algal blooms? Not sure if I believe it's all weather causes. In any other country first suspect would be illegal discharge of sewage/ industrial wastewater. Don't appreciate AVA/ NEA's opacity on these issues and water quality monitoring reports.



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