Beleaguered beavers are fishermen’s friend, claim scientists

For years, they have been accused of destroying Scottish fish stocks with their habitual dam-building. But a new study suggests that, on balance, beavers’ behaviour may actually be making life better for wild salmon in Scotland.

The research by scientists at the University of Southampton suggests that the overall impact on fish of reintroducing European beavers is more positive than negative. While the creatures’ dams do block fish from reaching local spawning grounds in the short term, experts say the same dams also increase habitat diversity, creating new areas that attract other wildlife which many fish feed on and providing refuge for them during periods when river levels fluctuate.

As a result, there are more fish which are more productive, according to the study. It was based on a review and an opinion survey of fisheries managers, scientists, and beaver ecology experts across Europe and North America.

More than half (58 per cent) of the 49 experts who responded believed that the overall effect of beavers on fish populations was positive.

Researchers admitted that the study, funded by Scottish Natural Heritage, was surprising – a view shared by the Salmon and Trout Association which questioned the validity of the work.

Lead author Dr Paul Kemp, a researcher in freshwater fish ecology and fisheries management at the university, said: “Most participants were from a fisheries background and whom you might expect would tend to side with the fish but, based on their experience of beaver and fish interactions, tended to be positive towards beaver.

“The positive findings were more frequently based on quantitative evidence, while discussion of negative impacts was often speculative,” he added.

Beaver reintroduction has been a contentious issue in Scotland since 16 of the creatures were released in Argyll in 2009 and 2010 as part of a scientific trial conducted by the Scottish Wildlife Trust, The Royal Zoological Society of Scotland and the Forestry Commission ­Scotland.

Further controversy surrounds the establishment of a breeding population of escaped beavers on the River Tay – prompting the Angling Trust to call on the UK government to launch an “urgently needed” cull of the animals to prevent them spreading to England where it is feared they could damage ­fisheries.

Salmon and Trout Association Scottish policy officer George Holdsworth said: “There is no question that dams from beavers can increase diversity. However, the real issue is if they are impeding the migration of salmon in some areas. Dams can stop fish moving.”

Querying the study’s focus, he added: “There’s also a fundamental difference between European and North American beavers in terms of the dams they create and their life cycle.

“They are different animals. I’m not saying this is bad science but the danger is that you 
can make a wrong conclusion [by comparing different 
species].”