Muscled out: Singapore's native green mussels face competition from foreign species

Muscled out: Singapore's native green mussels face competition from foreign species

Mytella Strigata, or charru mussel, is not native to Singapore and can be considered invasive.
The charru mussels are visually similar to the native green mussel, and differentiating them by eye can be a challenge. Their shells range from black to green, and are rimmed with bumps. (Photo: Fann Sim)

SINGAPORE: Singapore's native green mussels are at risk of being displaced by a competing species from the Atlantic waters near South America.

The Mytella strigata, commonly known as charru mussels, was first discovered in our shores by accident in 2016.

In the year since, these foreign mussels have reproduced rapidly, with sightings reported last year at eight other locations including Sungei Buloh, Sungei Jurong and Pulau Ubin, said a team of researchers at the National University of Singapore's Tropical Marine Science Institute.

MUSCLED OUT

At a research site at Changi fish farms, the researchers found that the charru mussels - which grows on hard surfaces such as seawalls and boulders as well as soft sediments like mudflats and mangrove floors - displaced native green mussels by taking over their space.

As part of their study, the researchers placed sheets of nets underwater and reviewed them on a monthly basis.

"What we see on our fishnets is that it's recruiting much, much faster than the green mussels. It'll reproduce. Once you sit first, and you occupy all the space then the other one cannot go in," said Dr Serena Teo, a senior research fellow at the research institute.

"They (green mussels) have less space to settle and grow bigger ... We know that the Mytella Strigata can choose to settle in many places and that also includes the spaces that the green mussels also likes to dominate," said research associate Lim Chin Sing. 

Invasive mussels discovered in Singapore as part of NUS study
The Mytella strigata, or more commonly known as charru mussel, was recently discovered in Singapore and is spreading rapidly. (Photo: Fann Sim)

"We do not know when it arrived in Singapore but what we have now is a detection when it has spread. Invasive species can come by many, many different routes. Through shipping, aquaculture, people also carry things around. There are a number of ways species can travel," Dr Teo added.

Dr Teo urged the public to not collect or consume charru mussels found in the wild.

Mussels are filter feeders that obtain nutrients by processing large amounts of water they live in. 

"While they are consumed in some countries, I think it's important in Singapore that people are a bit more cautious about what they want to collect. Wild collected food carries risk of environmental contaminants whereas what you buy from the market has gone through Agri-Food & Veterinary Authority (AVA)," said Dr Teo.

In the next phase of the study, the researchers will look into the life history of these mussels, such as their reproduction rate and environmental tolerance. 

The researchers will also look at the larger impact of their invasive presence on fish farmers and the shipping industry .

HOW DID THEY GET TO SOUTHEAST ASIA?

The earliest record of the charru mussel appearing in the region was logged from a specimen collected from the Philippines in 1800s.

"They could have travelled through the Spanish galleons, maybe like an attachment to the boat or maybe through aquaculture or things that they bring over. These Spanish galleons travelled from America to Philippines in the 16th to 19th century so it could have followed them there and established in the local estuaries in the Philippines," said Ms Lim Jia Yi, an NUS graduate who worked on the study. 

NUS researchers found 'alien' mussel in Singapore shores
Lim Chin Sing, Lim Jia Yi and Teresa Stephanie Tay are part of a team at the National University of Singapore who discovered an "alien" mussel which was recently introduced in Singapore and spreading rapidly. (Photo: Fann Sim)

The findings were published in the Molluscan Research journal.

Source: CNA/fs

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