Her video quickly drew similar reactions, with some people quipping that the fish were leaving en masse due to the country's cost of living.
Other residents said that the phenomenon was not new.
Inventory assistant Mohamad Salleh Saidali has seen this happening on occasions over the past few years, having observed the canal's biodiversity from the window of his flat.
"I have been watching them from time to time. They usually come when the tide is going up," the 43-year-old said.
The smaller canal along Canberra Street is connected to a larger canal along Yishun Avenue 8 and Simpang Kiri Park Connector that opens out to sea, from which the school of fish could have entered.
Residents have also seen otters romping and hunting fish in the canals.
The sagor catfish is a coastal species found near river mouths and tidal rivers with muddy beds.
Dr Karenne Tun, group director at the National Biodiversity Centre of the National Parks Board (NParks), told CNA on Monday (Dec 15) that it is amphidromous, which means that it migrates between freshwater and saltwater environments.
"Its ability to survive in both environments provides it with access to a wider range of food sources, and opportunities to escape from predators that are unable to tolerate changes in salinity," Dr Tun added.
A study on its reproductive biology in Vietnam showed that the black fish grows to more than 44cm.
The species is classified as being of "least concern" in the Singapore Red List published in the third edition of the Singapore Red Data Book, which documents Singapore's biodiversity to support conservation efforts.
This means that the sagor catfish has a stable population and is not considered close to threatened status.
Asked why the fish were in the canal, independent researcher Ng Heok Hee suggested that the school of subadult catfish could be feeding.
The ichthyologist who has studied catfish for about 20 years at the National University of Singapore said: "This species largely feeds on shrimps and crabs (with the occasional small fish thrown in), so canals may be a rich hunting ground for them.
"Despite being a relatively common species, the biology of H sagor is poorly understood. Results from some studies have suggested that the juveniles prefer higher-salinity waters.
"If so, this may be a large school that transiently enters freshwater for food. Another possibility may be that they are just following the tide as they swim up canals."
Dr Ng added that fish swim in schools for protection to avoid being singled out by predators.
Fellow ichthyologist, Dr Tan Heok Hui, said that the canal's hard, straight walls and lack of hiding places made it a "sterile environment" compared with the catfishes' natural riverine habitat.
On whether the species is edible by humans, Dr Tan said that anglers sometimes catch and then throw the catfish back because they "don't taste good".
"(Anglers) call them 'ah seng' and say that they smell and taste of dirty drains," Dr Tan added.
The sagor catfish has a venomous spine on its dorsal fin and on each of its pectoral fins, which are used to protect themselves against predators, Dr Tun from NParks said.
"Their stings can be excruciating and long-lasting. Members of the public are advised to take caution if they encounter catfish in the wild and to avoid handling them," she added.
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Other residents said that the phenomenon was not new.
Inventory assistant Mohamad Salleh Saidali has seen this happening on occasions over the past few years, having observed the canal's biodiversity from the window of his flat.
"I have been watching them from time to time. They usually come when the tide is going up," the 43-year-old said.
The smaller canal along Canberra Street is connected to a larger canal along Yishun Avenue 8 and Simpang Kiri Park Connector that opens out to sea, from which the school of fish could have entered.
Residents have also seen otters romping and hunting fish in the canals.
CATFISH SPECIES COMMON BUT "POORLY UNDERSTOOD"
The sagor catfish is a coastal species found near river mouths and tidal rivers with muddy beds.
Dr Karenne Tun, group director at the National Biodiversity Centre of the National Parks Board (NParks), told CNA on Monday (Dec 15) that it is amphidromous, which means that it migrates between freshwater and saltwater environments.
"Its ability to survive in both environments provides it with access to a wider range of food sources, and opportunities to escape from predators that are unable to tolerate changes in salinity," Dr Tun added.
A study on its reproductive biology in Vietnam showed that the black fish grows to more than 44cm.
The species is classified as being of "least concern" in the Singapore Red List published in the third edition of the Singapore Red Data Book, which documents Singapore's biodiversity to support conservation efforts.
This means that the sagor catfish has a stable population and is not considered close to threatened status.
Asked why the fish were in the canal, independent researcher Ng Heok Hee suggested that the school of subadult catfish could be feeding.
The ichthyologist who has studied catfish for about 20 years at the National University of Singapore said: "This species largely feeds on shrimps and crabs (with the occasional small fish thrown in), so canals may be a rich hunting ground for them.
"Despite being a relatively common species, the biology of H sagor is poorly understood. Results from some studies have suggested that the juveniles prefer higher-salinity waters.
"If so, this may be a large school that transiently enters freshwater for food. Another possibility may be that they are just following the tide as they swim up canals."
Dr Ng added that fish swim in schools for protection to avoid being singled out by predators.
Fellow ichthyologist, Dr Tan Heok Hui, said that the canal's hard, straight walls and lack of hiding places made it a "sterile environment" compared with the catfishes' natural riverine habitat.
On whether the species is edible by humans, Dr Tan said that anglers sometimes catch and then throw the catfish back because they "don't taste good".
"(Anglers) call them 'ah seng' and say that they smell and taste of dirty drains," Dr Tan added.
The sagor catfish has a venomous spine on its dorsal fin and on each of its pectoral fins, which are used to protect themselves against predators, Dr Tun from NParks said.
"Their stings can be excruciating and long-lasting. Members of the public are advised to take caution if they encounter catfish in the wild and to avoid handling them," she added.
Continue reading...