Sunday, September 2, 2007

The mussel beds in Chek Jawa

Something new appeared in Chek Jawa after the mass death early this year.

Huge patches of blackish slime looking thing were found covering huge areas of the intertidal flat.

They are usually found in the boundaries of the seagrass lagoon and the sandbars.

A closer look reveals holes in them which contains a tiny mussel with byssus threads around them, forming a mat of mussel bed over the whole area.

Gastropods like to eat these mussels. And we also bunches of pink and yellow stuff that looks like a carnation are actually eggs of a muricid snail.

And this is whole the shell of the mussel or also called the Asian date mussel looks like.

According to Joseph Lai, the person who discovered Chek Jawa, he shared that plenty of this smallish Asian Date Mussel can also be found around Pulau Sarimbun - right around the foot of the island as well as the nearby rocks of a shoal east of it.


From a couple of readups, this is what I got from journals (references below).

"The Asian date mussel, Musculista senhousia is an Indo-Pacific mytilid that was unintentionally introduced in the early 1990s in the north-eastern Adriatic Sea, and actually occurs with large populations also in Tyrrhenian (Gulf of Olbia) and Ionian (Mar Piccolo) coastal areas.

Mussels live semiburied in subtidal soft sediments, secrete byssal threads to attach to conspecifics, and build extended mats that alter the nature of the sediment inhabited by commercial infaunal bivalves."

Below are some FAQs for you to know more about them. They can't be ignored. Most of the facts are taken from NIMPIS, 2002.

What is its scientific name and classification?

Musculista senhousia. Phylum: Mollusca, Class: Bivalvia, Subclass: Pteriomorphia, Order: Mytiloida, Superfamily: Mytiloidea, Family: Mytilidae

What are their dimensions and how does it look like?

Maximum length of around 30mm and has a smooth, thin shell which is an olive green to brown in colour, with dark radial lines or zigzag markings.

In which part of the habitat can they be found?

From the intertidal to subtidal habitats (to a depth of 20m) and on soft or hard substrata. It prefers to settle in groups on soft substrata, but is capable of fouling wharf pilings and man made structures.

When settled on hard substrata the mussel will not form a protective cocoon. It is a highly adaptive species, and is able to tolerate low salinities.

In which part of the world can you find these mussels?

Native range: Russian Federation, Democratic People's Republic of Korea, Republic of Korea, Japan, China (CSIRO, 2000), Singapore (OBIS, 2006).

Known introduced range: USA (USGS, 2006), Canada, Mexico (Cohen, 2005), New Zealand, Australia (Allen and Williams, 2003), Israel, Egypt, France, Italy, Slovenia (CIESM, 2005), Tanzania, Madagascar (Mastrototaro et al. 2003).

What is byssus thread and what is it for?

It is used to construct a cocoon which protects the shell. This cocoon is made up of byssal threads and sediment.

How does it grow and reproduce?

M. senhousia is a species with high fecundity, rapid growth, a short life span and good dispersal ability, making it a successful invader.

It has separate sexes, with males and females spawning at the same time. The larvae of this species are planktonic, and have been recorded in the plankton for up to 55 days. It can reach an adult size in only 9 months, and its life span is typically no longer than two years.

How does it feed?

This mussel, like most mussels, is a suspension feeder. It consumes organic matter and many planktonic organisms from the water surrounding it.

What feeds them then?

Diving ducks and oystercatchers have been recorded feeding on M. senhousia, and it is also consumed by many species of carnivorous gastropods. In San Diego Bay, field experiments have indicated native gastropods may prevent M. senhousia from establishing dense beds.

What are its impact to our shores, like Chek Jawa?

It can dominate benthic communities and potentially exclude native species. It settles in aggregations and is therefore able to reach high densities.

The byssal mats formed by the mussel may restrict the growth of some species of seagrass.

The byssal mat may also cause an increase infaunal density and species richness as it provides additional habitat for many species.


1. Crooks, J.A. (1998) Habitat alteration and community-level effects of an exotic mussel, Musculista senhousia. Marine Ecology. Progress Series 162, 137– 152.

2. Mistri, M. (2003) The non-indigenous mussel Musculista senhousia in an Adriatic lagoon: effects on benthic community over a 10 year period. Journal of the Marine Biological Association of the UK 83, 1277– 1278.

3. Mistri, M. (2004) Prey preference of Carcinus aestuarii: possible implications with the control of an invasive mytilid and Manila clam culture in a northern Adriatic lagoon. Aquaculture 230, 261–272.

4. NIMPIS (2002) Musculista senhousia species summary. National Introduced Marine Pest Information System (Eds: Hewitt C.L., Martin R.B., Sliwa C., McEnnulty F.R., Murphy N.E., Jones T. & Cooper S.). Web publication

5. by Global Invasive Species Database

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