The cost of commercial salmon farming

For thousands of years Atlantic salmon ran freely through the rivers of the British Isles from the Thames to the remotest Scottish burn. Of course, the fish had its natural enemies – seals and sharks at sea and birds of prey and otters inland — out one predator, above all, effectively decimated its numbers in British waters.

Man’s ‘industrial progress’ turned many salmon runs into little more than toxic gutters, while overfishing and poaching accounted for huge numbers of sea and fresh water stocks. As a result, the price of salmon rose dramatically and demand far outstripped any natural supply.

Salmon saviour

The development of salmon farming was not only seen as a saviour of the suffering wild salmon but also of the Scottish angling market – reputedly worth millions to the nation’s economy. The farms boosted the tackle industry and tourism, and created a great many jobs.

The wriggling life-forms that emerge from the eggs are alevins. When their yolk sacs are used up these creatures become fry. The farmed fry are then overfed to speed up their growth to the parr stage.

commercial salmon farming

When the fish reaches the parr stage it is taken from the breeding stations to large cages, situated in fresh water lochs. Here it is again pellet-fed to excess, to advance its growth to the smolt stage.

Glimmer of hope

In 1816 Thames salmon were so common that they fetched only thrupence a pound at London’s Billingsgate market. By the 1840s, pollution had emptied the river of salmon. Now, 150 years on, salmon are starting to run up the Thames again.

parr stage salmon

In the wild the smolts migrate to the rich, more abundant feeding grounds at sea where they gain their silvery coat and large size. Farmed smolts are put into sea cages and fed pink food to colour the flesh.

harvested salmon The finished product of the commercial farm process is a harvested salmon that would grace any fishery. However, this fine fish is destined for the table – which means it is killed by a blow to the head, packed in ice and transported to a smokery.A female wild salmon is stripped of her eggs A female wild salmon is stripped of her eggs -which are then fertilized with the males’ milt. Fresh water is passed over the eggs for 70 to 100 days (depending on water temperature) before the alevins hatch.

The best by farm

Commercial salmon farming was heralded as a godsend – surely now the massive slaughter of the wild stocks would abate and the market price drop? Salmon farm-srs, working in almost laboratory conditions, artificially fertilize the salmon eggs and then feed the young fry as much food as they can take to ensure rapid growth.

When the farm-reared salmon reach the parr stage they are put into freshwater cages, and again automatically pellet-fed to fatten them up as quickly as possible.

Finally, at the smolt stage – when the wild salmon would start migrating to the sea — the young fish are transferred to sea cages. Here they are fed pellets charged with pink colouring to give the flesh its desired appearance.

As a result of salmon farming, the market price has dropped (even below that of cod) and the pressure on the overfished wild salmon has, to a certain extent, relented.

Too good to be true

This new style of farming has its good points, but little attention has been paid to the down side. Intensive feeding in the Scottish lochs has created its own pollution and the introduction of thousands of fish has altered the water’s chemical balance.

The surplus food that falls from the cages is gorged on by Arctic char – a fish that rarely grows beyond 2lb (0.9kg) in normal conditions. The char caught now around the cages are reaching weights of 9lb (4kg) and over. When this food source ceases the only way the char can maintain their unnatural large size is by cannibalism. As a result, there is a predominance of predators – putting even more pressure on, and depleting, existing natural fish stocks.

A selection process takes place before the smolts are transferred from fresh water to salt water and the unacceptable salmon are released into the wild. These rejected fish follow their natural instincts and return one day as mature fish to spawn. But they are genetically inferior to the wild fish without the same inbuilt immunity to disease.

The problem comes when the wild and the farmed salmon cross-breed. There is bound to be a diluting of the wild strain, leading to even more inferior fish, more vulnerable to infection and disease.

Problems also arise in the sea cages where lots of salmon in a small area is a breeding ground for sea lice. The use of pesticides to treat the lice-ridden fish doesn’t only kill the pests – it also affects all the other aquatic life in the surrounding area.

A possible solution is to try more natural treatments. For example, using one of the species of ‘cleaner’ fish such as goldsinny -which feed on lice and other fish parasites -to keep the salmon lice-free. Unfortunately the cost of researching such methods may not appeal to profit-motivated farmers.

It’s up to us

It is to be hoped that we are waking up to the need for our waterways to be cleaned and the wild salmon stocks preserved and encouraged. If we aren’t careful, the day will come when an artificial lake is the only place left to catch this king of fish – or his less noble, farmed cousin.

At the end of the day there must be a compromise between unfettered commercial gain – with no consideration for the environment – and the need to maintain and improve on stocks of wild salmon. Given the will, there’s no reason why salmon farming could not be a great help in this.