Shellfish

Since 2016, a new species of mussel that could have come from as far away as the Americas has been spreading rapidly along Singapore's northern coast, clogging up nets in fish farms and displacing the Asian green mussel native to Singapore, as they compete with the local molluscs for space.

Observed in clumps of up to 10,000 individual shellfish, the invasive American brackish-water mussel has also been forming dense mats in the Kranji mudflats - home to rare horseshoe crabs - to the dismay of nature groups here.

Invasive species such as the American mussel could hurt also Singapore's status as a top transhipment hub globally. The Republic, like many coastal cities with urban harbours, is vulnerable to invasions by such shellfish.

When invasive mussels attach to hard surfaces, they form clumps in places such as on seawater intake pipes and vessels. Such undesirable marine growth on man-made surfaces is known as biofouling.

These clumps can reduce vessel speeds by more than 10 per cent due to drag, and increase fuel consumption of ships when they power up to overcome it. Such marine pests can also damage engines and propellers

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

Some mussels can live for up to 50 years

The mussel’s ‘beard’ is known as the byssus. It is used by the mussel to attach itself to surfaces with the aid of a secreted adhesive cement.

Before preparing a mussel for cooking and eating, the byssus should either by cut off or pulled out with a sharp tug, then discarded.

Mussels are usually prepared by steaming over a medium heat for about six minutes or until the shells open.

Because mussels contain liquid that emerges during the steaming process, you don’t have to add water when you’re steaming fresh mussels.

You shouldn’t be concerned if a batch of mussels is of different colours: pale white meat indicates a male mussel, and a warmer, more orangey colour, a female.

Mussels affix themselves to substrata such as rocks by their byssal threads or ‘beards’. These are produced as a liquid, which sets in contact with seawater.

The byssal threads are so adhesive they can even cling to Teflon; scientists are trying to develop a mussel-based adhesive for use in eye surgery

These bivalves filter the water that passes into their shells and absorb the phytoplankton, which are the "plant drifters" of the oceans.

The growers began switching from the raft method of cultivating mussels in favor of a modified Japanese longline system. The current process uses this modified longline system even out in open waters. Spat, the seeds or eggs from the female mussels, are seeded on the ropes where they attach themselves with threads formed by a special secretion.

The mussels grow on the ropes, filtering phytoplankton from the water and mature reaching between 9-12cm (3.5-5 inches). The mussels require no food or feeding which means that their entire process leaves no impact on the environment. The do not eat something that is needed by other sea creatures and there is always an abundance of these phytoplankton.

Green mussels can be easily harvested from floating blue barriers or from the intertidal flats at low tide

This delightful 'fat' little conch snail is often seen on many of our shores, on silty and sandy areas with good seagrass growths. Although large, these snails are well camouflaged. It was previously known as Strombus canarium. 'Canarium' means 'dog' in Latin, and it is sometimes also called the Dog conch.

Where common it is commercially harvested for food in many parts of Southeast Asia. In the Philippines, the shells are traditionally used by fishermen as sinkers for nets.

Like other creatures of the intertidal zone, they are affected by human activities such as reclamation and pollution. Trampling by careless visitors and over-collection can also have an impact on local populations.

Eggs hatch after four days and the planktonic larvae (known as veligers) drift with the current for between 14 to 60 days. After reaching lengths of about a half-inch, they sink to the sea bottom and hide.

Conch Shells in History: In Mayan art large conches were used as paint and ink holders for scribes, as bugles and hand weapons.

In Cayman, before the age of telecommunication, conch shells were used as a signalling horn by native fisherman to communicate with other boats and with villagers onshore. Elsewhere the conch shell was used as a horn in times of battle or at celebrations

Abandoned conch shells are used by marine creatures, such as the cardinalfish and octopus, as protection from predators.

It has an unusual means of locomotion that is common only among the Strombidae. This curious series of maneuvers was originally described by American zoologist George Howard Parker in 1922. The animal initially fixes the posterior end of the foot by thrusting the point of its sickle-shaped operculum into the substrate. Then, it extends its foot forward, lifting the shell and throws it ahead in a motion that has been described as "leaping"

Imposex has recently been detected in L. canarium.[43] Imposex is the development of male sex organs in female animals exposed to man-made organic tin compounds, such as tributyltin (TBT). It has negative consequences for several species of sea snails, ranging from sterility in some individuals to the extinction of entire populations.[44] Tin compounds are biocidal antifouling agents mixed into paints to prevent marine encrustations on boats and ships. High concentrations of these compounds are commonly present in seawater near shipyards and docking areas, exposing nearby marine life to harmful effects

Dog Conch can be easily harvested from the intertidal flats at low tide.

Another seafood favourite, in Singapore, these clams are also called 'la-la'. Venus clams are still commonly seen on some of our shores, in sandy and rocky areas near seagrasses and coral rubble.

The two-part shells are thick. Some have ridges or various patterns. They are usually buried just beneath the surface. The fine ridges on their shells to help them stay buried.

Like many other bivalves, venus clams are filter feeders. They lie buried in the sand and extend their siphons to the surface at high tide. They use their siphons to suck in water and filter out microscopic food. The water also brings fresh oxygen to the animal

A clam's oval-shaped shell pieces are hinged by a stretchy ligament. The front of the clam's body features a muscular foot that the clam can extend through the open end of its shell for burrowing into the sand or mud.

the clam's body has two siphon-like tubes. Clams feed and breathe by drawing water and food particles into one tube and expel waste-filled water out the other

Some clams are among the longest-lived species in the world. For example, in 2007, scientists discovered a specimen of the ocean quahog that was between 405 and 410 years old.

The phrase "warmed the cockles of my heart" has been the subject of much amusement and intrigue since MP Jamus Lim used it to thank Sengkang GRC voters after they elected his Workers' Party team into Parliament in the recent general election.

Used to convey a sense of contentment and delight, it is actually a reference to the heart's ventricles, or Cochleae cordis, and not real-life, sun-loving cockles that can be found on Singapore's shores.

Photosynthetic algae living in their flesh harness sunlight streaming through the water to make food in a process known as photosynthesis

And as filter feeders, they can help cleanse the water column, by filtering out nutrients and other larger particles.

Blood cockles have always been a widely available source of protein in Singapore. They get their name from their red flesh, caused by high levels of haemoglobin. And their slightly metallic flavour makes them a delicacy – like oysters, but cheaper

No more 'hum' in laksa? Why cockles are becoming costlier and harder to find

In 2013, Singapore imported 2,720 tonnes of cockles from Malaysia, the source of more than 99 per cent of the Republic’s live cockles

Cockles spend their lives burrowing in the muddy seabed not far from the shore, and Malaysia’s coastline was once a fertile breeding ground, thanks also to its relatively slow currents.

But its cockles are dying off because the natural balance of their habitat is being disturbed. “It’s because the water is contaminated by acid, or chemicals are released into the water, causing pollution and harming the cockles,

The Thais love cockles as much as the Malaysians do, but their coastline does not produce enough to meet the demand. That is why the smuggled spat can go for as much as five times the price in Malaysia.

Plastic nanoparticles - plastic pieces smaller than 1 micrometre - have been found to accumulate in certain marine organisms and could be transferred up the food chain, according to a study by scientists from the National University of Singapore (NUS).

The NUS research team looked at smaller pieces of plastic - nanoplastics - using barnacles and their larvae to understand how nanoplastics could impact marine organisms.

Barnacles may be at the lower levels of the food chain, but what they consume will be transferred to the organisms that eat them

Barnacle swims only short time after hatching and spends the rest of its life attached to the hard surface

Besides for rocks, shells and boats, barnacle can be also seen glued for the body of whales, turtles, crabs and other sea creatures. Most animals are not even aware of barnacles on their body because they do not produce harmful effects.

Barnacle is an omnivore. Its diet is based on plankton and algae.

Barnacle is filter-feeder. It collects small particles of food from the water using its feathery appendages (modified legs).

Larvae of barnacles generally swim in the water for 6 months or more, until the animals find a permanent surface that they attach to via the head, using antennae and a glycoprotein based mixture

They secrete a fast-curing cement that is among the most powerful natural glues known, with a tensile strength of 5,000 pounds per square inch and an adhesive strength of 22-60 pounds per square inch. The glue is so strong that researchers are trying to figure out how it can be used commercially.

Barnacles attach themselves to buildings and boats, which can be both hard to remove and damaging to the object, and can cause significant speed loss in boats.

The U.S. Navy estimates that heavy barnacle growth on ships increases weight and drag by as much as 60 percent, resulting in as much as a 40 percent increase in fuel consumption!