Mussel invasion

06 March 2018 | Research
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The invasive species, Mytella strigata, was first observed by the researchers in March 2016

A research team from the Tropical Marine Science Institute (TMSI) at NUS has successfully identified the presence of an invasive mussel species in Singapore. Originally from the Atlantic and Pacific coast off South America and the Pacific coast off Central America, the mussel, identified as Mytella strigata, was found along the north-west coast of Singapore and on floating pontoons in the East Johor Straits.

A routine field trip investigating pest mussels in March 2016 was when the team first came across the unfamiliar small dark-coloured mussel. Later that month, while collecting juveniles of Perna viridis — the Asian green mussel native to Singapore — from fishnets placed underwater at the Changi fish farm, they noticed an increase in the number of these same unknown mussels, with an accompanying decrease in the Asian green mussel. Each month, up to 10,000 Mytella strigata mussels were observed on a small net measuring about 30cm by 25cm, showing signs that they could be displacing the native Asian green mussel.

“An invasive species is an animal that grows so fast that it has economic impact,” explained Dr Serena Teo, Senior Research Fellow at TMSI and co-supervisor of the research team. She shared that the Mytella strigata observed on the fishnets indicates that it is reproducing much quicker than the green mussel.

“They are competing for the same space, but sometimes the Mytella strigata is faster so it appears in larger numbers compared to the green mussels which have less space to settle or grow,” added Mr Lim Chin Sing, a Research Associate at TMSI.

This could adversely affect fish farmers who sell the much larger green mussel, said Dr Teo, although she cautioned that more work needs to be done in other habitats to fully understand the broader picture and determine any possible economic impact.

They are competing for the same space, but sometimes the Mytella strigata is faster so it appears in larger numbers compared to the green mussels which have less space to settle or grow.

Identifying the mussels involved extracting their DNA and comparing the sequences against known sequences in the imaging bank. “We realised that Mytella strigata is genetically not very related to Perna viridis, although they look similar,” said Miss Lim Jiayi, an NUS Biological Sciences alumna who worked on the project.

Armed with this knowledge, TMSI Senior Research Fellow Dr Tan Koh Siang, co-supervisor of the project, made a trip to the Natural History Museum in London to look into the historical records of mussel shells. This endeavour allowed the team to clarify the species’ name and origins. While at the museum, Dr Tan uncovered records which suggested that the Mytella strigata could have been first discovered in Asia in the Philippines in the 1800s. 

“They could have travelled by way of the Spanish galleons, maybe as an attachment to the boat or maybe through aquaculture or things that they brought over. The Spanish galleons travelled from America to the Philippines in the 16th to 19th century so it could have followed them there and established in the local estuaries, remaining undetected until recently,” Miss Lim elaborated.

From the Philippines, they could have then made their way to Singapore.

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From left: Mr Lim, Miss Lim and TMSI Research Assistant Miss Teresa Stephanie Tay who worked on the project, with some of the mussels 

While this particular species of mussel is collected and consumed in countries like Brazil, the researchers cautioned against doing so.

“Wild collected food carries risk of environmental contaminants, whereas the food you buy from the markets has gone through screening by the Agri-Food & Veterinary Authority of Singapore,” Dr Teo said.

The researchers will soon be looking into the life history of the mussel — its ecology, growth rates and environmental tolerance. They will also be looking into the impact of the invasive species on the shipping industry and how to address it.

The findings of the research were published in Molluscan Research in February.