Water temperatures damaging fish stocks in two of our most famous rivers

Extra.ie​

2 days ago

Water temperatures are damaging fish stocks in two of our most famous rivers, marine scientists have discovered.
At Lough Feeagh in Co. Mayo the highest temperatures in 70 years, when recording began, have been seen.
Sea temperatures off the western and southern coasts were so high they constituted a marine heat wave and some of our most famous salmon rivers – the Moy and Erriff – were closed due to the escalating warmth in the water which is stressful to fish. Cows on the shores of Lough Feeagh, county Mayo, Ireland. Pic: Shutterstock
Lough Feeagh provides a testing area for biologists from the Marine Institute, who have been monitoring the rising temperatures and observing how Atlantic salmon have been adapting.
Marine biologists Dr Elvira de Eyto and Dr Joshka Kaufmann explained how warming of the seas will affect Atlantic salmon.
They collect water samples for testing and carry out analyses 'pretty quickly'. Dr de Eyto explained to RTÉ's Countrywide that the lake is probably one of the most monitored in Ireland by accident.
'The lake would be monitored by the Environmental Protection Agency and also by the Marine Institute as (both) have a long history there since the 1950s. Water temperatures are damaging fish stocks in two of our most famous rivers, marine scientists have discovered. Pic: Shutterstock
'The two channels here lead out to the Atlantic and every migratory fish such as Atlantic salmon, brown trout and European eel,' she Rivers said. All three of the fish closed: types are counted by the Atlantic.' staff of the Marine Institute salmon twice a day.
'We need the environmental data to support the fish data such as water temperature, the oxygen in the water, the chemistry of the rivers, the food sources – all the things that might change how a fish is reacting.
'Data was taken in 2015 as part of global lake temperature collaboration and one of the papers we used showed signs of warming, and now 10 years on in 2025 we see that rate increasing.
'It shows that the water temperature is increasing 0.2 degrees per decade. The scientists had seen the water temperatures increasing late last month when it was warm for the time of year. Pic: Shutterstock
'That is 1.4 degrees in seven decades. And [with] our winter warming by 0.3 degrees, we are not seeing those really cold temperatures which are needed,' Dr de Eyto said.
The scientists had seen the water temperatures increasing late last month when it was warm for the time of year.
'We were seeing temperatures of 15, 16, 17C degrees in the hatchery where we run some breeding programs which are really high for May and much higher than we would expect and the temperature off the coast was three degrees warmer than normal.
'What was happening at sea was being mirrored in Lough Feeagh,' Dr de Eyto said. 'The warmest months are August or September and the coolest February or March. This year the colder months have not really cooled the water as much as we would have liked to see.
'All these ecosystems are not separate; they are all interlinked from the top of mountains right out to the Atlantic.'