GBS bacteria found in two types of fish: What you need to know about them

The toman fish, or snakehead fish, is one of the two fish types flagged by MOH for having traces of GBS bacteria.
The toman fish, or snakehead fish, is one of the two fish types flagged by MOH for having traces of GBS bacteria.ST PHOTO: FILE
The Song fish, or the Asian bighead carp, is one of the two fish types that has been found to contain traces of GBS bacteria. In 2007, the fish were found in the Sungei Kadut canal, and foreign workers who lived in the area caught them.
The Song fish, or the Asian bighead carp, is one of the two fish types that has been found to contain traces of GBS bacteria. In 2007, the fish were found in the Sungei Kadut canal, and foreign workers who lived in the area caught them. PHOTO: COURTESY OF KATE YONG

The article was first published on July 27, and updated on Nov 27, 2015.

SINGAPORE - Food stalls will no longer be allowed to sell Chinese-style raw fish dishes - including raw fish porridge - unless they can show that the fish is from safe suppliers, the authorities said on Friday (Nov 27).

They confirmed that there is "an association" between eating Chinese-style raw fish dishes and what appears to be an aggressive strain of Group B Streptococcus (GBS) bacteria known as GBS Sequence Type (ST) 283.

This strain has caused serious infections in several people who had eaten raw fish dishes this year. 

According to tests conducted by the authorities on nearly 400 fish samples, ST283 was detected in 4.1 per cent of the samples - in Toman fish, also known as Snakehead fish; Song fish, also known as Asian Bighead Carp; and Tilapia.

The first two types are used by food stalls selling Chinese-style raw fish dishes. Tilapia is usually not eaten raw. It is safe to eat the three types of fish as long as they are fully cooked.

Here are some facts about the three types of fish.

Song fish, also known as Asian bighead carp

How much does it cost?

In Hokkien, it is known as "songhe". It costs about $6 per kilo, according to Mr Khor Chin Puang, who owns fresh fish wholesaler Pan's Fish and has been in the fish retail business for eight years.

How popular is it?

While it is cheap, demand from consumers is "almost non-existent", and it is usually hawker stalls and restaurants that buy this type of fish. Mr Khor said that several shops in Chinatown sell steamed Song fish in black bean sauce. It is also used in raw fish porridge.

Why is it eaten?

Dr Tan Heok Hui, a fish expert from the department of biological sciences in National University of Singapore (NUS), said that the Song fish is highly esteemed for its head region, used in steamed dishes. There is a section of fish fats and oils below the cranium which is "highly delectable", he said.

Where is it from?

The Song fish is originally from riverine and lacustrine waters in northern Indochina and southern China, Dr Tan said. It has been imported usually as young fishes to be cultivated or to be grown out in mud ponds for aquaculture and for food fish purpose. The Song fish is a filter feeder, feeding mainly on suspended plankton.

Toman fish, also known as Snakehead fish

How much does it cost?

In Hokkien, it is known as "loyhe". It costs about $24 per kilo, according to Mr Khor.

How popular is it?

It is highly esteemed for its firm white flesh, Dr Tan said. It is used for tonic food, san lao hor fun and steam boat. The fish is now often available as chilled or frozen fillets.

Why is it eaten?

Mr Khor said that the Chinese believe that the fish has medicinal properties. It is usually given to people who have undergone surgery or just given birth.

Where is it from?

It is originally from the South-east Asia region, found in rivers and lakes. It is a highly territorial and predatory species feeding on smaller fish and other organisms. It is usually cultivated as a cage fish or in mud ponds, and imported as fillet for the food market.

Tilapia

How much does it cost?

Tilapia costs about $6 per kg, said Mr Khor.

How popular is it?

It is sold fresh in the local wet markets and supermarkets, as whole fish, as fillet, as frozen teriyaki fillet, said Dr Tan.  Some consumers shun it as they complain it has a muddy taste, but the meat is tender and not fishy.

Why is it eaten?

In restaurants, it is usually served as steamed fish, fried fish, sweet and sour fish. It is even served as sashimi in some affordable sushi joints, said Dr Tan.

Where is it from?

The fast growing tilapia originated from Africa, but is now found all over the world. It is known in the food business as “aquatic chicken” because it is easy to cultivate.

It is a freshwater fish that is farmed in freshwater ponds or cages in rivers. There is also sea tilapia, which commands a higher price. 

Most of the tilapia sold in Singapore come from local and Malaysian sources, Dr Tan said.

The hardy fish are not picky eaters and are cheap to farm. Some tilapia are even farmed with faeces, in an “active recycling of nutrients”. “ If hygiene and proper food handling techniques are employed, the fish is safe to eat, provided there is no chemical or heavy metal contamination,” said Dr Tan.