BivalvIA

Bivalves. Shellfish? Soap dishes? Jewellery? Currency? Do they have souls? Do they feel pain? Who knows? Whatever your persuasion, bivalves represent an easily accessible, zero-input source of protein and fatty acids direct from the sea. They filter plankton from the water column and convert them into tasty food.

Just as with plankton, shellfish are vulnerable to their environment, since they not particularly picky as to what they ingest. Shellfish poisoning, while feared by most in fits of mass hysteria, is not as common as you’d think. You’re more likely to get noro virus from beef as you are from eating shellfish. Either way, shellfish should only be cultivated in pristine waters away from any human pestilence. Properly processed bivalves are purified (or depurated) before consumption, which makes them mostly safe to eat, especially in months without an “R” in them.

Bivalves are quite easy to cultivate, are low maintenance and improve the surrounding marine environment, making them ideal for co-location with fish farms to hoover up all that uneaten food and organic matter. A no brainer, if you ask me (or do they have brains?)

Native Oyster (Ostrea edulis)

Like most bivalves, these elusive oysters are masters of disguise. Also known as European flat oysters (not pictured left, but similar), they’re extremely sensitive to their environment and infections such as Bonamia ostreae, which, along with pollution and ocean acidification, has led to a significant decline in native oyster numbers around the British Isles. However, there are a number of restoration projects popping up, in particular those run by the Native Oyster Network. Further projects are underway around Bournemouth on the South Coast and Craignish in Scotland, which also combines seagrass meadow restoration in another win for the environment and biodiversity.

Ostrea edulis can be found in estuarine and shallow coastal water with hard substrata of mud and rocks. They are prized for their unique tannic seawater flavour, sometimes described as dry and metallic. They are generlaly eaten fresh but can also be cooked in the same way as mussels.

Having first evolved almost 16 million years ago, the Romans used to ship British oysters back to Italy by the bucketload. However, in modern times they aren’t as popular for commercial cultivation as their tougher cousin, the Pacific oyster Crassostrea gigas.

Pacific Oyster (Crassostrea gigas)

The beefy American cousin of the native flat oyster is much more robust than it’s fair-weather friend. They are the most commonly cultivated species of oyster in the UK, mostly on trestles or beds in Class A intertidal areas.

The seed from the wild (‘spat’) can either be collected by the removal of seaweed from beaches or by hanging shell (cultch bags) in suspension from long lines in the open water. The oysters can be fed live feed in the form of phyto- and zooplankton or copepods, which also need to be cultivated.

The movement towards hatchery-reared spat is important, as wild seed is susceptible to changeable environmental conditions, such as toxic algal blooms, which can halt the supply of seed from that region.

Even this tougher cousin of the oyster is sensitive to its environment, which maykes oyster farming a risky business. Farming under hatchery conditions provides more control, but pollution from human activity and extreme weather events can wipe out whole colonies overnight.

Razor Clams (Ensis magnus / arcuatus)

Razor clams or razor shells are at the cutting edge of bivalvery. They are as old as time itself, having barely changed in millions of years. Besides their distinctive shells, they can be recognised by a key-shaped hole in the sand at low tide. Most people use the old trick of pouring salt into the hole to coax them skyward. It’s then when you see their remarkable muscular foot which they use to bury themselves in the sand.

Mostly harvested by hand by bonkers divers in all weathers, they may also show potential for cultivation and commercialisation as a delicious amuse-bouche.

Clams & Cockles

Clams and cockles are another poor man’s food with a long tradition in the British Isles. They can be easily gathered at low tide with a rake, and cooked in the same way as mussels. They are a fantastic addition to a cullen skink (i.e. seafood broth) or a pasta alle vongole if you’re feeling Italian.

Similarly, avoid eating them in the summer months and you won’t go far wrong. If you really mean business, you can purge them in seawater or even tap water for a few hours so they expel any nasties before cooking.

Scallops

Scallops: the shellfish no-one really knows how to pronounce in English. There are two varieties in the British Isles, King (Pecten maximus) & Queen (Aequipecten opercularis). They have 30-36 eyes, can swim and are apparently attracted to light. They are also delicious, known to some as the ‘chicken of the sea’. Since you only eat the adductor muscle (i.e. the ‘foot’) and sometimes the roe (reproductive organ), they are usually a safer bet than other shellfish which are consumed warts & all.

Most scallops are caught by dredging or trawling the sea bed, a highly antisocial behaviour which should be banned outright. Free diving for scallops is a much more sustainable and envigorating approach.

Blue Mussels (Mytilus Edulis)

No web page about shellfish would be complete without the mighty Mytilus edulis (picture not necessarily to scale). Historically known as the ‘poor man’s food’, blue mussels are an abundant species that can be found clinging to rocks with their byssal thread - once treasured by the Romans as ‘sea silk’, being woven into a fine cloth for the rich and famous. It has even been suggested that the Golden Fleece sought by Jason & the Argonauts was made from this magic material.

Legends aside, moules frîtes are an unbeatable dish in those long winter months. Cooked in a creamy white wine sauce with parsley you can’t go wrong. Best eaten with an ‘R’ in the month (i.e. not in the middle of summer) as bacteria are most abundant at that time of year.

These filter feeders have been cultivated for centuries, and can play a big role in the recycling of nutrients and “cleaning” the water column.