By Richard Black
Environment correspondent, BBC News website
The magnificent salmon leaps from a foaming river like a glittering acrobat.
The lobster patrols the reef, the mussel clings to its wave-rinsed rock; the tilapia finds shelter in weed fronds at the lake's edge.
These are not chicken or pigs or cows that stand where we tell them, eat what we give them and evolve as we breed them.
No; taste seafood, and you taste the wild. Presumably this image is part of its appeal.
If so, it is an image which is rapidly falling out of step with reality because the proportion of our seafood that is farmed is surprisingly big, and growing fast.
"The latest figures of the UN Food and Agriculture Organization (FAO) say it is close to 50%," observes Patrick Sorgeloos, an aquaculture specialist from the University of Ghent, and an advisor to the FAO.
"It is about 60 million tonnes; and the FAO is indicating that by the year 2030 we will need an extra 40 million tonnes just to satisfy the need."
Given the parlous condition of many of the world's fish stocks, it is tempting to see aquaculture as the answer - a source of healthy protein which the oceans can no longer guarantee.
Governments and regional authorities from the industrial might of Norway to rural Africa see it as the way ahead.
"The potential to expand the catching of fish is getting limited," notes Sloans Chimatiro, fisheries advisor to the New Partnership for Africa's Development (Nepad), an initiative of the African Union.
"But also the products that come out of the lakes and oceans, because of the cost involved in catching them, become very expensive and so unaffordable for the local community.
"So growing fish is going to enable the continent to produce fish that is affordable."
It is not a view shared by everyone.
"Aquaculture has got a big potential value for food security, it's revenue for communities and it's an alternative food source," concedes Simon Cripps, director of the marine programme at the conservation group WWF.
"But the thing to remember is that it isn't the solution to the problem of wild-caught fisheries."
Environmental groups lodge a long list of grievances against aquaculture.
Shrimp ponds destroy mangrove forest, a natural shoreline protector, and leave land too saline to use again. The waste excreted by concentrated masses of fish or shellfish wreak havoc with local ecosystems.
Fish, especially salmon, escape from their cages and breed with their wild cousins, weakening their genetic stock and ability to survive and reproduce.
Carnivorous species such as salmon and cod have to be fed on food made from wild fish such as anchovies, depleting stocks still further.
Connemara in western Ireland is a cragged, peaty landscape where time seems to hang in the air like a fine mist.
As a holiday destination it boasts music, walking, cycling, and traditionally superb Irish hospitality; but for many, the first attraction is fishing.
"Tourism is easily the most important industry here now," says Peter Mantle, "and a crucial part of that industry was the fishing that derived from the clean waters and the unpolluted countryside."
I am standing with Peter on the banks of a small, urgent river near his property, Delphi Lodge, a centre for anglers.
The rivers here are famed for their salmon. But there are fewer, he believes, than in former years; and he believes salmon farms are the culprit.
Salmon naturally carry a parasite, the sea louse. Packing them into cages gives the lice a permanent home; overcrowding stresses the fish, making them still more vulnerable to infestation.
There is a wealth of evidence now, some from scientists in Europe and more from Canada, showing that lice harboured in farms materially damage wild stocks - something that Peter Mantle believes is happening before his eyes.
In spring 2006, he released a number of baby salmon from his hatcheries. All were tagged; half were treated with an anti-louse chemical before release, half were not.
"This year we're beginning to get some of the adults back, and we've just finished reading the tags of the first 80 to return," he relates.
"Sixty fish came from the treated group, and 20 from the untreated group. So even the most elementary maths implies that two out of three of the untreated fish that would otherwise have made it back have been killed by sea lice."
Faced with criticism over their environmental record, some arable and livestock farmers have responded by moving to organic methods.
Aquacultural farmers are following suit.
"When we sell our fish as organic, we are charging a very big premium for that," says Gerry O'Donohue from the Mannin Bay Salmon Company, also in Connemara.
"And that premium recognises the fact that we have low stocking densities, we use fish foods that come from traceable and sustainable sources, and all of our records in relation to every step of the process are subject to rigorous audit."
He says that following a set of fairly simple rules can keep lice at bay. Areas are left fallow in some years, fish are given more room to move, and a seaweed-based compound is added to their food which makes their skin produce mucus, which lice do not like.
"We don't want sea lice either," he notes.
Patrick Sorgeloos admits that aquaculture does have its share of problems, but thinks we should not be too surprised given the speed of its development.
"Science is proving that we can develop solutions, but we do not have them yesterday," he reasons.
Finding better ways to farm is one way to make the industry more sustainable. Others include switching to species that do not have problems such as sea lice, siting farms with more ecological sensitivity, and developing feeds that do not mandate the catching of wild fish.
Some of that work is highly technical, based in laboratories, involving molecular sciences and even genetic engineering.
Farming mussels is regarded as environmentally benign
But other ideas are out there, apparently dangling before our eyes.
Wrasse, for example, will eat pretty much anything, even sea lice. So why not put them in with the salmon? They are guaranteed a supply of food, and the salmon will be healthier too.
It is being tried and even implemented in some farms.
Why not farm species that thrive on a vegetarian diet? It is being done, notably in Africa with tilapia.
And why not farm combinations of species that help each other, the first producing waste which is food for the second - a version of a natural ecosystem?
Despite the reservations of some farmers, this too is happening.
"In coastal aquaculture in China, there is an area of several hundred square kilometres where there is integrated farming of mussels, scallops, seaweeds and fish," says Dr Sorgeloos.
"That is what we are trying to bring to Europe now. Because the salmon farmer of the future, be it in Chile or in Norway, they have to use an ecosystem approach in order to be sustainable on a long term basis."
There is no doubt that the first wave of modern aquaculture has brought problems. Science and regulation have trailed behind entrepreneurship, and authorities have sometimes courted the industry when they should have been checking up on its credentials.
Doubtless more problems will arise. But is there any method of food production, from arable farming to livestock to hunting and fishing, that can claim a perfect record?
Patrick Sorgeloos believes humanity is simply making the same logical transition now with seafood that it made with meat thousands of years ago: "We are moving from hunting to farming."
With wild fisheries in their current parlous state, we had better get used to it.
The rise of aquaculture is discussed further on the current edition of One Planet on BBC World Service