Predation and beavers


A number of animal species prey upon wild trout — mammals (e.g. otter, mink), birds (e.g. cormorants, sawbill ducks) and other fish (e.g. pike, larger trout). Predation is just one of a complex of natural factors impacting on wild trout populations; for many populations the effects of unsympathetic land use, poor in-river habitat, low water quality and water quantity, and poor river management regimes will be of greater significance.

WTT recognises that predation can be problematical for fish populations and for fishery interests. From the 1970s through to 2000s, there was an increase in the inland over-wintering population of cormorants and an increase in the geographical range of goosanders, though evidence for the last 20 years suggests that numbers of both have stabilised or even slightly decreased.

Read this article by Andrew Griffiths, first published in Fly Fishing and Fly Tying magazine in 2019.

Unequivocal, scientifically-derived information establishing direct relationships between wild trout and predator populations in aggregate is lacking and difficult to obtain, especially for rivers. However there is anecdote from various parts of the British Isles indicating effects of intense, localised predation pressure from piscivorous birds.

For the Wild Trout Trust position & advice, please click the link below:
Avian predation information paper

We believe that the primary focus for fishery interests in tackling predation problems should be the creation and maintenance of complex and varied habitat that gives fish a much greater chance of avoiding predators. 

Fishery interests can additionally deter predators through a range of scaring and/​or exclusion techniques, though these may be more applicable to small stillwaters rather than rivers or large lakes and their efficacy relies on persistence and variety of scaring method.

Cormorant S1 H9022 Carms
Cormorant drying it's wings after diving. Photo: Melvin Grey


As with all (re)introductions of species, the case of the Eurasian beaver (Castor fiber) is generating much heat in the UK media from many angles: conservation, fisheries, natural flood management to name but a few. There are now several trial schemes in place spanning from the Tamar in Devon to Tayside in Scotland.

The majority of questions we at WTT get asked regarding beavers involve passage issues for wild trout around dams. While any ecological interaction between two species is inherently complex and influenced by locality and flow régime for example (in this particular case), we should remember that beaver and trout have co-evolved for millennia and coexist in many locations throughout Europe. However, the landscape throughout much of the UK where they might formerly have coexisted, prior to the extirpation of beaver, has changed considerably and is now subject to a suite of environmental pressures from humans that could influence the outcomes of any current interaction. We have reviewed the scientific literature and numerous reports from other organisations. Click on the links below to read the summary paper or full paper:

Wild Trout Trust beaver-trout interactions: summary

Wild Trout Trust beaver-trout interactions: full report

Note – neither report considers management options in any detail. 

The Eurasian Beaver Handbook: Ecology and Management of Castor fiber , published in 2016, contains a comprehensive overview of management issues by one of Europe’s leading experts, Róisín Campbell-Parker. 

Scottish Natural Heritage have provided guidance on the management of beavers in Scotland. 

The River Otter Beaver Trial in Devon concluded early in 2020. The final report is available here. The Management Strategy Framework published as a result of the study on the River Otter is available here.

Former WTT Conservation Officer for the South West region, Mike Blackmore, sat on the Fisheries Forum for the Devon Wildlife Trust Beaver Trial. The role of that forum is to ensure that fish and fisheries stakeholders (e.g. angling clubs) are engaged throughout the study and have the opportunity to ask questions and raise any concerns. Mike wrote a very interesting article on the River Otter Beaver Trial for us in 2019, available here

Beaver female with kits 1 M Iike Symes comp
Beaver female with kits. Photo: Mike Symes