Just before cooking, soak your mussels in fresh water for about 20 minutes. As the mussels breathe, they filter water and expel sand. After about 20 minutes, the mussels will have less salt and sand stored inside their shells.

Reproduction. Both marine and freshwater mussels are gonochoristic, with separate male and female individuals. Freshwater mussels reproduce sexually.

Much like clams, mussels are cooked live. Like most fresh shellfish, mussels may still have sand or barnacles on them, so wash them well before cooking. Many may also have a bristly thread called a beard, which helps anchor them to rocks in the ocean.

The beard isn’t harmful or inedible (just not particularly desirable to our taste buds), so don’t fret if there are a few little threads left that you can’t grasp. With a bit of practice, cleaning and debearding a few pounds of mussels should only take about 15 minutes of your prep time.

Barnacles and white worm grow on the outside of mussels’ shells. To remove, scrape off with a blunt knife then rinse quickly under cold water.

Place the mussels in a colander in the sink and run water over them, using your hands or a clean scrubbing brush to rub off any debris like seaweed, sand, barnacles, or mud spots that could be on the shell. If you find any mussels with open shells, lightly tap that mussel against the side of the sink.

When submerging the steamers in the water, watch for any that float—this means that they’re already dead and should be discarded. (Note that when preparing mussels, the opposite is true: They clamp shut tightly, trapping air in the shell, and therefore should float when alive. Discard any that sink.)

Mussels must be alive to ensure their freshness and their shells should be closed to make sure they are alive. If any are open, they should close when tapped or squeezed.

The ‘R’ rule states that shellfish, such as oysters and mussels, should only be eaten in months with an ‘r’ in their title, otherwise they are unsafe to consume.

Peak season for fresh mussels is October to March. You can buy mussels in their shells year-round from the chiller cabinet, or, ready shelled versions come frozen, smoked and bottled in brine or vinegar.

It has been known for a long time that consumption of mussels and other bivalve shellfish can cause poisoning in humans, with symptoms ranging from diarrhea, nausea, and vomiting to neurotoxicological effects, including paralysis and even death in extreme cases.