Beavers and fish
FINDING A BALANCE
Working to realise the ecological benefits of beaver activities while protecting and preserving migratory fish populations.
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Our freshwater fish populations play a vital role in maintaining ecosystem health, but they exist in a perilous state with over one third of species facing extinction.
Wild Atlantic salmon, a keystone species, are in crisis, having declined by 70% in the last 25 years. The population in Great Britain is now classified as endangered due to to the latest species reassessment by the IUCN Red List of Threatened Species, announced at COP28 in December 2023.
Fish face a multitude of existential threats, from polluted waterways, overfishing and habitat destruction, to over-abstraction of water for irrigation and over 23,000 man-made barriers in waterways in Britain blocking migratory passage.
The reintroduction of beavers—a keystone species—has a potentially transformative impact on these ecosystems. Their engineering can create a diversity of habitats, improved areas for rearing and overwintering, refuge from predation, strong currents, and temperature increases, as well as increased insect production.
However, concern remains on the ability of beaver dams to impede movement of migratory species to and from their spawning grounds at critical times of year. While the impacts are highly dependent on the specific site and species, and will change over time it is perceived to be a further threat to migratory populations.
At Beaver Trust we are working hard to design pragmatic management schemes and contribute to scientific research so we can realise the ecological benefits of beaver activities while protecting and preserving endangered migratory fish populations.
Our Work
In 2022 we started a multi-year project collaborating with other organisations to collect baseline data on fish populations at potential beaver sites prior to their release which will hopefully allow us to answer numerous questions about the impacts of beavers on migratory salmonids following any habitat modification.
In collaboration with the Wild Trout Trust, Atlantic Salmon Trust, Westcountry Rivers Trust, and Devon Wildlife Trust we’ve adapted the findings from our Restoration Manager, Dr Rob Needham’s PhD into a training resource to help people better understand the potential interactions between beavers and migratory salmonids.
A wider information pack is currently being developed by this group which will provide more information on salmonid and beaver ecology, migration, and how the species interact.
Our Experience
Dr Rob Needham is an experienced field biologist with over a decade of experience with beaver projects since starting as a field officer at the Scottish Beaver Trial in Knapdale in 2009
His PhD through the University of Southampton investigated the interactions of beaver habitat modification on brown trout populations in Scotland.
The first publication related to his PhD came out in 2021 and showed that beavers had profound effects on the local brown trout population that promoted higher abundances of larger size classes. It is still the only publication to date that has researched the impacts beavers have on salmonids in Britain.
A further publication is expected later in 2024 into the wider impacts of beaver habitat modification on brown trout.
Rob also undertakes semi and fully quantitative electro-fishing surveys in a variety of habitats which are tailored to specific requirements as part of his work as Beaver Trusts Restoration Manager.
The Science
Watch Dr Rachel Malison of Flathead Lake Biological Station, part of The University Montana, give an extensive review of the literature relating to fish and beaver interactions. Exploring the co-evolution of beavers and salmon, why local context is very important and the complexity of ecological systems.
Dr Malison originally gave this presentation at our inaugural beaver conference in 2023 in Exeter, but was commissioned to record it by the Cairngorms National Park Authority as part of the Cairngorms Beaver Project.
If you’re eager to delve deeper into the research on beaver and fish interactions, explore our science database, which offers access to over 500 scientific publications on beavers, all conveniently available in one place.
