Trout and salmon are among the world's most familiar freshwater fishes, but numbers have fallen over recent decades in some areas, dramatically.
Pollution, habitat loss and over-fishing have all been blamed in the past, but new evidence from Cardiff University shows that climate change could be a major factor, putting both species at risk.
The scientists studied populations of young salmon and trout in the River Wye in Wales, traditionally one of the UK's best angling rivers. Professor Steve Ormerod and colleagues from the Cardiff School of Biosciences found salmon numbers fell by 50% and trout numbers by 67% between 1985 and 2004 - even though the river itself became cleaner.
The fish were hit hardest following hot, dry summers such as 1990, 2000 and 2003. The results suggest that warmer water and lower river levels combine to affect both species. As both trout and salmon favour cool water, they face potentially major problems if climate warming continues as expected in the next two to three decades.
"Huge efforts have been put into bringing salmon back into Europe's formerly polluted rivers such as the Taff, Thames, Clyde, Seine and Rhine, so these results are a major worry," said Professor Ormerod.
"Salmon and trout fishing also generate many jobs and large economic benefits. In Wales alone, salmon fishing contributes around 90 million annually. Any risk of eventually losing these species to climate warming is therefore one we must consider very seriously. We suggest measures to ensure that river levels are maintained in hotter conditions alongside the use of riverside trees to create shade and protect against the highest temperatures. This week's Wales Sustainability Week is an ideal opportunity for us to consider action for Welsh rivers, particularly because trout and salmon are such important sustainability indicators."
The Cardiff team used data on fish population collected each year by the Environ
|Contact: Professor Steve Ormerod|