''Are you," asked my best friend when she heard I was going to write this piece, "going to scare more people with your tales of salmon?" You see, despite being a greedy carnivore, not objecting to smoking in between meals and having no known food allergies, I am an unwelcome guest at the dinner table. I started becoming unpopular four years ago when I stopped eating salmon. Then, a great many people were still unaware how unhealthy farmed salmon could be: thus it would invariably be served. I would try to be discreet and not get into discussions about why I'd just have extra vegetables, thank you. But once or twice, when some other guests wouldn't just "leave it" as Grant Mitchell would say, I would be forced to justify myself. And then, I'm afraid, I took rather perverse pleasure in telling them the full horrors of what they were eating.
I can understand why I'm so unpopular. It's not that people don't want to be educated about their food, but they're tired of being told that just about everything they eat is bad for them. The reason I've picked the salmon to champion is that, because of my job, I spend a large part of my life in a wild salmon's natural habitat. I fish for salmon but in such a way that I can have all the fun of the fishing without ever catching any. It gives me an excuse to stand in salmon rivers, learning about my beloved salmon and talking to people who knew long ago that the wild Atlantic salmon was as endangered as fluffy little pandas. In some parts of the world, Atlantic salmon numbers are down by 99 per cent. To give you more of a local idea, one season, in a little river in Scotland, 700 smolts - young salmon - went to sea and none came back the following year to spawn.
The reasons given for this vary - depending on whom you ask and who pays their wages. It's a little bit of lots of things: environmental changes, pollution, commercial fishing, damming. All of these contribute, but, to my mind, the real murderer of the wild salmon is the very thing that was sent to save it: farmed salmon. In the past 20 years, stocks of wild salmon have halved. Although aquaculture has been around for thousands of years, salmon farming only really became commercial 20 years ago. As recently as 1991, UK production of farmed Atlantic salmon stood at "just" 41,000 tonnes. But by 2000 it was more than 124,000. As we produce more farmed salmon, there are fewer wild salmon. Today, aquaculture is the world's largest growing food industry. One in five fish we eat is farmed.
In the 1970s, farmed salmon barely existed. Salmon was still a wild, seasonal delicacy. As stocks of wild salmon started to decline due to over-fishing, it was farmed salmon to the rescue! And what a good idea it seemed. Big cages of salmon could be "grown" on the seashore, it would provide local jobs (it still does, the salmon farming industry is the most important economic development to have happened to the Highlands and parts of western Scotland and provides employment for several thousands), it would take the pressure off the wild fish stocks, provide a more consistent product and everybody would be happy.
The reality is different. There is big money to be made (in Scotland alone, the retail value of farmed salmon is £600m a year) and so competition is fierce. Not all salmon farms are bad - this is important to remember. Some really do try to be responsible, and more on this later. But, our many salmon farms are owned by just a few companies - it's feared that, in five years' time, just a handful of companies will control 90 per cent of all salmon production.
Salmon farms that care little for fish or environment and bow to Mr Dollar cram thousands upon thousands of salmon into sea-cages - the average stocking density is 20-25kg per cubic metre of water, but this is just what's admitted to. The wild salmon is an aggressive, carnivorous, turbocharged animal. He's built to swim, sometimes hundreds of miles a day; not in circles. In the wild, a salmon grows at his natural pace - going to sea to fatten himself up aged two or three, and returning to spawn after one to three years of feeding in the oceans. In a salmon farm, his environment - light, feed, genetic selection - is manipulated so that he can grow as big and as fast as possible, often from egg to plate in as little as three years.
In such a crowded environment, disease is a problem, just as it is in the wild. The difference is that in the wild a sick fish can be solitary, not forced to rub fins. The really big problem is sea-lice. These are naturally occurring parasites that look like giant sperm. Their trailing egg-strings detach to produce more than 1,000 larvae, which will then look for more hosts. In the wild, salmon will be bothered by a few of them, which will drop off not long after the fish returns to fresh water. But the cages where salmon are farmed are a heavenly breeding ground for sea-lice. The farmed fish, protected by chemicals, shake them off. The problem is that the wild salmon smolts - small and without the "privilege" of such pesticides, have to swim past these cages to get to open sea (salmon farms are placed in coastal areas often near to where wild salmon run). You can imagine what joy the sea-louse must feel at the sight of such unprotected, juvenile flesh. It must be just like Stringfellows. They crowd the little fish, often congregating on his head to form a "death crown", eating into him until he weakens and dies. He never gets to see the wonderful feeding grounds off Greenland where he could have grown fat on prawns. He never gets to go back to the very gravel patch in the river where he was born, to sire more salmon. He floats to the bottom of the ocean, the sea-lice tails detach, and float away to find lunch elsewhere.
A farmed salmon is fed on pellets made up of a heady cocktail of antibiotics, dye, oil and meal made from inexpensive smaller fish like sardines and mackerel. It takes more than three kilos of these smaller fish to produce one kilo of farmed salmon. The processed fishmeal is often full of toxins that come from human industry - PCBs, dioxins, even flame retardants. Thus, when we sit down to eat a slice of lovely farmed fish, we gobble back our very own filth.
Does this mean we can never eat salmon again? No, farmed fish in general is here to stay, so we need to make wise and informed choices if we are to think long-term. Look for organic salmon; it'll still be farmed, but most of the issues raised in this piece will have been addressed. To get Soil Association accreditation, organic fish farms have to adhere to strict guidelines: stocking density is no more than 10kg per cubic metre, the fishes' diet cannot contain any artificial dye or growth hormones, and sea-lice are treated with hydrogen peroxide, which has little environmental impact, but it's expensive and requires expert handling -which is why it is not used more often.
Of all the supermarkets, I think that Waitrose has the most responsible fish policies; it is the only retailer that sells salmon from its own sites, at stocking densities of no more than 15kg per cubic metre. But whichever supermarket you buy from, if there is a fishmonger's in store, buy from there rather than pre-packed; the better-quality fish tends to go on ice rather than under cellophane.
Farmed salmon, when irresponsibly raised, is a horrible product. Its fatty, bloated, hump-backed flesh riddled with sea-lice, its tail savaged in frustration by its brethren, show us all too graphically the result of our greed for cheap "posh" fish at any cost. And yet, unless we do something to shun it, we deserve what we get.
Annalisa Barbieri is the fishing columnist of the Independent