Wild salmon are on the brink of disappearing from Irish waters

Irish Times

28-06-2025

It's difficult to grasp two truths when only one is in plain sight. Take a walk down the chilled section of any supermarket and you'll spot rows upon rows of Atlantic salmon for sale. Whether it's fresh, poached, smoked over peat or skinless, canned, in pots flavoured with lemon and herbs, or ready-made sushi rolls wrapped in rice, farmed salmon might not be cheap, but it's abundant, in high demand (Irish production has risen by 51 per cent in the past few years) and everywhere.
The other reality, underwater and hidden from our view, couldn't be more different. In the past five decades,
wild salmon numbers in Irish waters have dropped by 90 per cent
– and that's from an already low level in the 1970s. They are now on the brink of disappearing.
Earlier this month, scientists from Nasco, an international body set up in 1984 to protect these iconic fish, met in Cardiff. Known for their cautious, measured tone, the boffins' latest warning is anything but:
wild Atlantic salmon are in crisis
, and only 'urgent and transformative' action can save them.
Wild salmon are born in freshwater, travel to the sea, and then return to their birthplace to spawn, making them a clear sign of how well we're managing to coexist with other life. They need cold, clean and free-flowing waters, but right now we're offering rivers and oceans that are too warm, polluted, exploited or physically altered, making life impossible for these fish. On top of that, many rivers are blocked by man-made structures like weirs, culverts and dams, preventing salmon from completing their journey.
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Nasco scientists say that
salmon farming is a significant threat
. Along Ireland's west coast – from Donegal to Mayo to Cork – tens of thousands of salmon are raised in circular open-net cages that float just offshore. For sea lice, the crustaceans about the length of a small button that feed on salmon, these pens are like a giant seafood banquet. The lice attach themselves to the fish using their clawed limbs, then crawl across their skin, feeding on them and eventually eating through to the muscle and fat before releasing eggs into the surrounding waters. Without treatment, an infested farmed salmon won't survive long.
For young wild salmon leaving their home river for the first time, the journey to sea is full of danger. A female adult salmon lays thousands of eggs, but only a few will survive to become adults. As the young salmon swim by the salmon farms along the coast out into the Atlantic, they can pick up sea lice. These parasites can cause serious harm; scientists say it only takes a few lice to kill a young wild salmon.
However, some experts sharply disagree over how much blame sea lice from fish farms deserve for the decline in young wild salmon. This debate really matters because, by law, every fish farm must have an aquaculture licence to operate. The rules are clear: if the science raises any reasonable question that sea lice from a farm could cause serious damage to wild salmon, then granting a licence becomes very difficult for the authorities to justify.
'Unless a salmon conservation programme is initiated, Ireland could be looking at a situation where we will have little or no salmon left in the wild,' according to Declan Cooke of Inland Fisheries Ireland
Scientists can use a simple method to determine how sea lice affect wild salmon. They take two groups of young salmon; one group is given a special chemical treatment to protect them from lice; the other is left untreated. Both groups are then released into the same river, go to sea and face the same conditions. A year later, researchers count how many fish from each group return. If more of the treated salmon come back than the untreated ones, it shows that sea lice have a serious impact.
Between 2001 and 2009, scientists from the
Marine Institute
carried out this 'paired release' research at eight sites in Ireland. Their conclusions, published in 2013: while sea lice cause a 'significant' number of deaths among young wild salmon, the overall impact is 'minor and irregular'. This paper has been used to support the granting of fish farm licences as evidence that sea lice from farms aren't a significant threat to wild salmon survival.
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Wild salmon are an Irish icon. Now they're almost gone
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Not everyone agrees. Scientists from Canada, Norway and the UK raised serious concerns about the paper and, last month, researchers from
Inland Fisheries Ireland
published a new study looking at 18 years' worth of data from paired released experiments. They found that, on average, an 18 per cent drop in survival among young salmon that weren't treated for lice, and the more lice on the farms, the greater the losses. Their conclusion is clear: sea lice from salmon farms pose a real threat to wild salmon.
Why does this matter? Because 12 rivers along Ireland's west coast flow into legally protected areas where salmon farms operate. If scientists are now saying that these farms are killing young wild salmon due to sea lice infestations, then the law leaves little room for inaction. Authorities are obliged to act to move the farms to new locations, revoke their licences or find a way to ensure that there are no lice on the farmed salmon during the critical time when the young wild salmon are heading out to sea.
There is no single solution that will save Ireland's wild salmon. If emissions remain high, our waters will continue to heat up. But not everything is hopeless – there are things in our immediate control. We can remove our barriers, free our waters from pollution and, if the science shows it will help wild stocks survive, change how or where salmon farms operate.
Holding on to the reality of wild salmon in our waterways is one we should cling to – for future generations if nothing else.