Winter weather 'confuses salmon'

By Martin Cassidy
BBC NI environment correspondent

Irish salmon stocks are being hit by the effects of climate change with scientists on the river Bush in north Antrim discovering warmer winters are triggering a false start to the annual migration with disastrous consequences.

Warmer winter weather is confusing the salmon

It is the king of fish but even the mighty salmon is feeling the heat generated by climate change

And on the river Bush scientists say that warmer winters are confusing the young salmon.

Believing it is springtime, the juvenile fish are leaving the safety of the river and heading out to sea where many perish.

Richard Kennedy, one of the scientists at the Bush Salmon Station, says the timing of the annual migration of the young fish is crucial to their chance of survival.

"Ten years ago the first smolt that would have left the river Bush would have done so towards the middle to the end of April, but that seems to be changing and now first departures can be as early as the beginning of March," says Richard.

Out in the Atlantic, life is bleak for those young salmon.

Greedy gulls have quickly learned that the migration is now starting up to six weeks earlier and see the trickle of young fish as easy prey.

Migration

Nature intended migrations to be concentrated so as to give predators a narrow window of opportunity.

But now the seals are also picking off the young salmon as they head out into the Atlantic.

Usually around a third of the young fish which leave the river Bush survive to return here the following year to spawn

But now with warmer winters triggering a false start to the migration, only six in every 100 salmon make it back here to breed.

And that's not the only problem facing the river Bush. Climate change is also hitting the salmon in another way.

High rainfall is also swelling the river in winter and early spring, washing the delicate salmon fry away.

Gerscham Kennedy of the Bush Salmon Station has been recording increased spring flows and says that heavy rain in April is a particular problem.

People in Bushmills remember their river thronged with fish but in just 30 years the salmon stock has registered an alarming decline.

Last year, only 1,000 fish made it back here to spawn.

And like other rivers, the salmon in the Bush now face yet another man-made challenge.