Mr Rosman Mohamed has been fishing for leisure for almost 30 years, but a catch 10 days ago is his biggest yet.

On May 20, a Saturday, a video of the deliveryman and his companions hauling in an 8kg catfish from Rochor Canal in the late afternoon went viral.

The 45-year-old, who lives in Geylang Bahru, has been going to Rochor Canal to fish regularly since his wife died last year. He says that the average catfish he catches in the canal usually weighs 1kg or less.

Many online commenters expressed surprise that such a large fish could be found in what used to be a drain filled with rubbish on the periphery of the Central Business District.

It was not the end of the story. Mr Rosman and his friends, Mr Mohamed Affindi, 35, and Ms Aqidah Sarah, 19, went back to the same spot to fish the next day at around the same time and caught another larger-than-average fish, this time weighing 5kg.

"I was really shocked," the avid angler tells The Straits Times. "I was happy enough to get the 8kg fish on Saturday, but to get another big one the next day was a real surprise."

Mr Rosman, who spent more than $100 on his fishing equipment, uses chicken meat bought from a nearby supermarket as bait.

There are plenty of catfish in the canal, he says, and he and his friends once caught up to 22 of them in one session. They have also caught other species, such as tilapia, there.

Tilapia is the only fish that Mr Rosman, who has no children, will bring home to cook for himself. He does not eat catfish and gives them, including his two large prize catches, to foreign workers who mill around the area.

"Some of them offered me money for the big catfish, but I just gave them away for free. It's 'rezeki'," he says, using a Malay term that, among its many meanings, refers to food, sustenance or blessing.

He noted that in the days after his video went viral, the number of anglers at the canal jumped by about 10. He would typically see only a handful there during his fishing visits.

While Mr Rosman's haul usually ends up on someone's dinner table, there are others such as fishing enthusiast Sadat Osman who release the fish back into the water after he has caught them.

The 31-year-old, who is head of digital content and strategy at music publication Juice, spends at least two hours a week fishing with his friends all around Singapore.

"One day, my mother asked me 'you go fishing all the time but never bring back any fish'. So I brought back some peacock bass. She tried cooking them with sambal, but the meat tasted bad. I never brought fish back home again," he says with a chuckle.

And while the bachelor has gone on overseas fishing expeditions, Mr Sadat says that you can get large catches in Singapore waters. Prime fishing hours, he says, are "first light", from 6.30 to 8am, and "last light" from 5.30 to 7.30pm.

Several of his more significant hauls here include a 1.2m-long, 7kg barracuda caught in the north-east of Singapore, as well as the highly prized peacock bass, native to the Amazon Basin, measuring about 50cm long and weighing 6kg, from a reservoir in the central part of Singapore, he says, not wanting to reveal his secret fishing spots.

There are also those who venture farther for saltwater fish in Singapore waters, such as Mr Anthony Zhong.

Once a month, the 34-year-old bartender and co-owner of local bar Good Luck Beerhouse and his friends rent a boat to fish in the sea off the island.

Renting a boat with a skipper that fits about 10 passengers cost them about $650 for a day-long fishing trip from 7am to 5pm.

Mr Zhong's prize catches so far are a 7kg barramundi caught in the waters around Pulau Ubin and a 3kg golden trevally from the sea around Singapore's Southern Islands.

"We usually bring them to a restaurant in Punggol, have the cook there deep-fry one half and steam the other half and eat them immediately. There's nothing like eating freshly caught fish," he says.

But to catch the real giants in Singapore waters, one would have to venture even further to the waters off Pedra Branca, the eastern-most point of Singapore. In 2014, The New Paper reported that a restaurant owner here caught a whopping 172kg, 2.3m-long Queensland grouper in the waters there. It took eight people to lift the fish and three hours to clean it before it was cooked and sold to the restaurant's customers.

One year earlier, The Straits Times reported another giant of the same specimen also caught off Pedra Branca that was 2m long and weighed 270kg. It took a forklift and seven men to lift the fish into the kitchen and more than 10 hours of cleaning before it was served to customers at a seafood restaurant.

There have been plenty of other reports detailing fishermen's giant catch - including a 2.75m-long guitar shark caught in the waters near Changi Naval Base near Bedok in 2009. Marine experts have also been quoted as saying that many species of large marine animals such as the whale shark, sawfish, billfish and false killer whale can be found in Singapore waters.

Big catch or not, fishing is a growing sport here.

In September last year, The Straits Times reported that more Singaporeans are picking up fishing as a pastime, thanks to new techniques and more fishing spots islandwide.

The number of users in angling forum Fishing Kaki, for example, has doubled to 450,000 in the last few years while sellers of fishing tackle equipment report that sales have gone up by about 20 per cent from 2013.

There are also more than 20 legal places to fish in mainland Singapore itself, including at reservoirs and waterways, jetties and waterfront parks and pay ponds.

In September last year, national water agency PUB opened up new fishing areas along Geylang River, Pelton Canal, Rochor Canal and Kolam Ayer ABC Waterfront at Kallang River under a one-year trial.

Because reservoirs and waterways are "common spaces to be shared among various users", according to PUB's website, anglers are allowed to fish only at designated areas there and have to abide by rules that include using only artificial bait at reservoirs. Those caught flouting the rules may be fined up to $3,000.

Mr Affindi says that fishing is the ideal sport for releasing stress, a point echoed by Mr Rosman.

"Fishing keeps me calm," says Mr Rosman. "It's one activity that teaches you patience."

Five large species of fish caught in Singapore

1 CATFISH

According to the National Parks Board (NParks) website, several types of catfish can be found in Singapore, most of which are native here, including warty catfishes and old world river catfishes. The two catfish caught by fisherman Rosman Mohamed at Rochor Canal were likely walking catfishes and weighed 5 and 8kg.

2 PEACOCK BASS

A prized catch among anglers here, the species hails from the Amazon Basin and was released into local reservoirs by aquarium hobbyists and is considered an invasive species that competes with native species for food and shelter. It can grow up to 74cm long.

3 GIANT SNAKEHEAD /TOMAN

Like the peacock bass, the giant snakehead, also known as toman, is considered an invasive species and was introduced into local reservoirs. It can grow up to 1m in length and weigh as much as 15kg.

4 BARRACUDA

Barracudas can grow up to 165cm long and can be found in the waters around Singapore and in the Southern Islands.

5 GROUPER

Giant groupers weighing up to 270kg and measuring up to 2.3m long have been caught in the waters near outlying island Pedra Branca, the eastern-most point of Singapore.

Correction note: The caption for picture featuring Mr Anthony Zhong has been corrected. We are sorry for the error.