Beavers benefit fish by building dams in Scotland

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image: Beaver swimming.
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Credit: R Needham

Alteration of riverine habitat by Eurasian beavers helps fish in small upland streams, according to a new study from the University of Southampton.

Research shows that by building dams in shallow waterways, beavers create deeper pools that increase the availability of suitable habitat and the abundance of food, which benefits brown trout, which is a commercially and ecologically important species.

Due to beaver activity, trout tended to be larger, having grown well throughout the year, with the larger and more mature fish, which are of most interest to anglers, being much more abundant. . In the modified habitat of the beaver, the trout also benefit from a refuge from predators.

The research, conducted by scientists at the University of Southampton and published in the Canadian Journal of Fisheries and Aquatic Sciences, monitored fish that inhabited two Scottish streams in Inverness-shire that flow into the same loch. One stream has been altered by beaver activity through the construction of five dams, while the other has not been altered, providing a unique opportunity to compare the influence of habitat alteration beaver on fish.

PhD student Robert Needham, from the Southampton International Center for Eco-hydraulic Research, explained: spawning grounds, as well as an impact on habitat quality. This study explored how brown trout respond to beaver activity.

Beavers were once common throughout the UK until they were hunted to extinction around the 16th century. As is the case in many countries in Europe, beavers have recently been reintroduced to the UK, with the first attempt at reintroduction taking place in Scotland in 2009. Today, they are again considered an element. nature of Scottish wildlife and are now protected. However, as they have been absent from the UK landscape for so long, there is little data on how they may affect other flora and fauna, including economically important freshwater fish.

Professor Paul Kemp of the University of Southampton, responsible for the project, said: “This is the first published research of this type to be conducted in the UK. Most of our understanding of beaver-fish interactions is based on North American studies that involve different species of beaver and different species of fish. The results of this study are important because it is hoped that they will allay the fears expressed by some representatives of fishing interests that beavers could harm fish stocks.

The project was carried out in collaboration with the Game and Wildlife Conservation Trust (GWCT), Salmon and Trout Conservation and NatureScot. The results are important as reintroductions and natural recolonizations are accelerating in Scotland, England and Wales.

Dylan Roberts, Head of GWCT Fisheries, said: “We welcome the results of this work published in the UK which is so badly needed to inform what is currently a very topical debate. The fact that many larger trout have responded positively to the ponds created by the beavers is good news. However, much remains to be learned to see whether their dams impede the upstream migration of adult salmon and trout on their way to spawning grounds and the downstream migration of juvenile fish.

Dr Martin Gaywood, NatureScot’s Species Project Manager, said: “We continue to work with stakeholders, including fishing groups, to identify the many complex ways in which beavers interact with our environment, to leverage the take advantage of the many benefits beavers can bring to nature and to us, and explore ways to alleviate the problems if necessary. This research is an important contribution to this process.

The article ‘The response of a brown trout (Salmo trutta) reintroduced Eurasian beaver population (Castor fiber) habitat modification ”was published in Canadian Journal of Fisheries and Aquatic Sciences: https://doi.org/10.1139/cjfas-2021-0023

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Notes to Editors

  1. For more information or interviews, please contact Peter Franklin, Media Relations, University of Southampton. Phone. 07748 321087 Email: [email protected]
  2. Robert Needham was funded by the NERC SPITFIRE Doctoral Training Partnership (DTP) hosted at the University of Southampton. SPITFIRE creates an innovative multidisciplinary experience for the effective training of future leaders in the fields of environmental science, engineering, technological development, business and policy.
  3. Game and Wildlife Conservation Trust: Providing research-driven conservation for a thriving countryside. The GWCT is an independent wildlife conservation charity that has conducted scientific research into Britain’s game and wildlife since the 1930s. We advise farmers and landowners on improving wildlife habitats. We employ 22 post-doctoral researchers and 50 other researchers with expertise in areas such as birds, insects, mammals, agriculture, fish and statistics. We conduct our own research as well as projects funded by contracts and grants from government and private organizations. The Trust is also responsible for several species in the Government’s Biodiversity Action Plan and is a lead partner for gray partridge and joint lead partner for brown hare and black grouse.
  4. The University of Southampton leads original thinking, transforms knowledge into action and impact, and creates solutions to the challenges of the world. We are among the top 100 institutions in the world (QS World University Rankings 2022). Our academics are leaders in their fields, forging connections with leading international companies and organizations, and inspiring a strong community of 22,000 exceptional students, from more than 135 countries around the world. Through our high-quality education, the University helps students on a journey of discovery to realize their potential and join our global network of over 200,000 alumni. www.southampton.ac.uk
  5. To learn more about engineering in Southampton, visit: https://www.southampton.ac.uk/engineering/index.page

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