On every rocky foreshore
Mussels are one of the most popular and iconic seafoods. They’re found all over the world but until 30 or 40 years ago, it was only in Europe that they were a mass market food. Now, thanks to a gigantic increase in supply from aquaculture, they're catching on elsewhere, especially China.
Almost everyone who has walked along a rocky British coast at low tide has witnessed countless thousands of small mussels clinging to the rocks in tightly packed beds. But these wild mussels are only a small fragment of the mussel industry because well over 90 per cent of all mussels sold for eating are farmed. However, without wild mussels' untold zillions of progeny, there would be no farming (see below).
Mussels have been farmed for centuries but serious commercial farming kicked off in the early 20th century, mainly in Spain and Italy. These two countries still dominate the business although the UK and Holland and are also now in on the act, and so are China (now the biggest producer), Chile and New Zealand.
FOUR MAIN SPECIES
There are many species of mussels but four account for the vast majority of commercial supply in Europe. These are Mytilus edulis, or the blue mussel, found around UK coasts. It’s a fairly small mussel, rarely exceeding 10 cms in length (lengths quoted are for wild mature mussels; farmed mussels are harvested at smaller sizes). In my experience, the blue mussel's shell tends to be thin and quite brittle. The Mediterranean mussel or Mytilus galloprovincialis is a bigger beast, readily reaching 15 cms and it has a tougher shell. It prefers warmer waters and is the dominant mussel from the northern coast of Spain into the Mediterranean as far as the Black Sea. This is The Fish Society’s preferred mussel.
Mussels from the west Pacific often have a green tinge along the opening edges of their shells. The New Zealand greenlip mussel, Perna canaliculus, is found along the entire coast of New Zealand and there is a major farming industry concentrated in the north. This is a much bigger mussel than the European species, reaching 20 cms before harvesting. Some say that consumption of this mussel helps sufferers from osteoarthritis and the key extracts are available in capsule form from health shops. However, there is little firm scientific evidence. The fourth mussel readily available in Europe is the Chilean mussel, Mytilus chilensis. It’s similar in size to the Mediterranean mussel.
|The renowned greenlip mussel from New Zealand. Quite a beast.|
FAO figures for 2015 showed that China produced about 700,000 tonnes of mussels, Europe - 550,000 tonnes, Chile - 240,000 tonnes and New Zealand - 100,000 tonnes. The global total was around 1.8m tonnes said to be worth about $3bn.
PROLIFIC OR WHAT?
For such small creatures, mussels produce astonishing numbers of eggs: 5 million for a 7 cm mussel, up to 40 million for a large mussel. Per year! Male mussels work even harder - they produce 10,000 spermatazoa per egg. The eggs are released as plankton, measuring a few hundredths of a millimetre and inevitably 95 per cent or more rapidly die or are consumed by other sea creatures including adult mussels. After a few weeks survivors settle on seaweed, the sea floor or capture devices such as ropes. Now they grow to a couple of millimetres in size, beginning to grow their byssus which attaches the mussel to its landing point (and is astonishingly strong and well-engineered - the picture is by courtesy of MIT). The chef knows the byssus as the mussel's beard. The mussel will now grow by up to a centimetre a month in good conditions.
The tiny settled baby mussels are known as spat and mussel farms collect wild spat each year to provide new crops of mussels. In New Zealand thousands of tons of seaweed covered with tiny mussels are collected from beaches and transported to mussel farms to keep them in business. In Europe the spat is often collected by suspending “hairy” ropes above wild mussel beds. The availability of spat varies tremendously and in poor years mussel farms suffer decreases in production for lack of spat. Given that demand for spat has risen rapidly over the last 20 years, there have been several attempts to establish experimental hatcheries.
Most mussel farms use ropes suspended from buoys or rafts to raise their spat to commercial size, which takes 12-24 months. A raft might carry as much as 30 tonnes of mussels with a rope supporting 20kg of mussels per metre. A minority of farms–especially Dutch–grow their mussels on the sea bed.
The pictures show "bouchot" (French for wooden stake) mussel farming in France and a New Zealand deployment of rope suspension farming.
Mussels are a healthy food and if cooked in a little water or herby broth, might even balance out the effect of an accompanying bowl of frites. They are particularly rich in vitamin B-12 (good for nervous system and red blood cells), selenium (immune system) and manganese (brain, nervous system and general metabolism).
|Moules frites averages out at almost healthy|
Mussel farming is pretty benign. Reviewing 20 sources of farmed mussels worldwide, the Monterey Bay Seawatch programme rated 12 with its top grade Best Choice and the other eight as Good Alternatives. Significantly, mussels do not require commercial feed – they get all they need by filtering 30 or more litres of seawater per hour. So you get an awful lot of protein for zero food input. Perhaps the main problem for mussel farms is public opposition to the visual impact of mussel farms on coastal scenery.
https://everwideningcircles.com/2018/06/26/mussel-reproduction/ fascinating video of freshwater mussel releasing its eggs