Life

Take on Nature: Salmon knowledge can teach us much

A hen salmon leaping a weir to head upriver to spawn on the River Boyne at the end of October

SWIMMING for hundreds of miles through churning oceans, up and over cascading waterfalls and against the current in roaring rivers, an adult salmon will sniff its way back to its birthplace.

Somehow this fish, after years of growing in the waters off the coast of Norway, will manage to ‘smell’ its way back to the same Irish river – sometimes the very pool – where it was born to spawn its own offspring.

Rather than trying to work out if we should have garlic sautee potatoes or champ to accompany our salmon with béarnaise sauce, we should ponder on the mysteries of the life cycle of this most mysterious of fish.

In Irish mythology the salmon was associated with wisdom. In one of our best known myths the bard Finegas spends seven years trying to catch the Salmon of Knowledge.

When he does he puts it on a spit to cook and tasks his young apprentice Fionn Mac Cumhaill to tend it, warning him not to eat it. But a splash of fish fat burns his thumb and Fionn sucks it to cool it down and all the hidden wisdom of the salmon enters him.

Like many myths, there is often a hidden message behind this story – those who seek out wisdom (Finegas) might never find it, while for those who are not seeking it (Fionn), it can come upon them accidentally.

But perhaps the mythology surrounding the Breadán Feasa (Salmon of Knowledge) is a relic of the ancient understanding that this is no ordinary fish.

While it spends its first two or three years as a freshwater fish, the young salmon’s entire metabolism is repeatedly transformed until it is eventually drawn downriver and into the open sea. Like a piscine Doctor Who, it regenerates numerous times.

Fertilised eggs are known as ova and develop into alevins, which live beneath the gravel at the bottom of a river and are dependent on the yolk sacks of their eggs for food.

Once they break through and begin to swim freely they are known as fry and of the tens of thousands produced by a salmon pair the vast majority become food for other fish, birds and otters.

The fry that survive grow into parr and at this stage their bodies change as their metabolism begins to adapt for the open sea. Transformed now into smolt, they swim from the rivers of Ireland and out into the open sea and northwards towards the seas of Norway and mature into full-grown Atlantic salmon.

Why Norway? And how is it possible to travel such vast distances and after years of growing and maturing to swim back to their birthplace to spawn and begin the life cycle again?

If we could somehow learn more about the ways of the salmon we might be able to fathom some secret of the universe. But there is a new threat and not just from anglers. In the past few weeks there have been reports of Pacific salmon appearing in Irish rivers.

These are believed to have escaped from Russian fish farms in the 1960s and to have colonised the Arctic coast and are now making their way further south.

There are fears that they could impact on our native species, in the same way that grey (North American) squirrels have forced out and spread disease among Ireland’s native reds, endangering their very survival.

Again it is an example of man-made impact on the balance of fragile and interlinked ecosystems. We too as a species are part of that ecosystem, a product of it, yet our constant tampering is causing it to change. Anyone with a bit of salmon knowledge should be alarmed by that.

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Life