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Beavers will harm salmon habitat says Tweed Foundation

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Wild fish interests are challenging the accuracy of statements by the pro-beaver lobby that beavers pose no threat whatsoever to salmon and sea trout populations. These claims are entirely demolished by the publication of an exhaustive forensic analysis by the Tweed Foundation of the available scientific research on the subject.

Beaver Dam in Estonia

Beaver Dam in Estonia


Nick Yonge, Clerk to the Tweed Commission, commented: "Over recent months we have become increasingly concerned by the continual and flawed statements declaring that beaver dams will have no negative impact on our native fish. A complete picture has hitherto not been presented and there has been a highly selective use of the available research. Unfortunately there is a great lack of understanding by those who wish to introduce beavers on numerous aspects of beaver and fish interactions. For example, there is complete ignorance of the conditions that salmon and trout require in order to leap obstacles".

Mr Yonge continued: "In order to set the record straight the Tweed Foundation has researched and now published the facts as they stand. The findings are detailed and factual. Whilst beavers are zoologically very interesting animals, that interest largely stems from their ability to change the habitat in which they live, from one kind to another, by making dams. These dams create instream ponds and flood the land above them. Whilst this suits some species, it does not suit our native fish which are mostly migratory and need to move up and down our rivers. Instream obstacles hinder that movement. Before embarking upon trials to introduce beavers, a full assessment is required of what their effects will be upon our rivers. There may be benefits but there will certainly also be damaging effects, such as to fish. To understand this properly we need to know what the capacity is for beavers in Great Britain, say in 50 years time, and then match that with the changes we know they can make. An estimate could then be made of the cost of controlling beavers which has to be undertaken in all other countries with mature beaver populations. Only then can a rational decision be made to introduce beavers to Britain or not".

Andrew Douglas-Home, Chairman of the Tweed Commission, added: "Beavers may well be resourceful creatures with beneficial implications for some species. However we are highly concerned that the pro-beaver lobby has thus far conspicuously failed to give informed responses to our fundamental concerns about the impact of beavers on migratory fish. The beaver protagonists have consistently maintained that beavers and beaver dams are entirely beneficial to fish populations. However this is simply not borne out by the available scientific evidence which the Tweed Foundation has now drawn together and published. The literature shows conclusively that beavers can have a severe negative impact on migratory fish - particularly their ability to access spawning tributaries - with inevitable consequences for future fish numbers and thus employment levels on Scotland's rivers". 

Mr Douglas-Home continued: "The Knapdale trial appears to be designed to answer none of the difficult questions posed by fisheries and other concerned organisations, and is therefore also designed so that it can be declared successful and then the beavers will be released. It is now time for those responsible for the proposed trial beaver introduction in Argyll - in an area where there are no migratory fish - to correct the erroneous statements they have made in recent months and acknowledge that beavers, if and when they become established in large numbers, will indeed have a detrimental effect on salmon and sea trout populations. If the Knapdale trial is to proceed, it must be on the basis of informed debate. In light of the uncertainties and the dangers to fish, we believe that the Government should give an assurance now that all the animals will be removed at the end to the trial - regardless of what limited conclusions may be drawn from the monitoring of the trial. Any unrestrained release of the trial beavers may well act as a catalyst for further releases elsewhere and the released beavers will spread, breed and eventually beavers will reach the whole of Great Britain with inevitable consequences for the future of our world renowned fisheries".

Dr Ronald Campbell (Biologist for the Tweed Foundation), who has analysed the relevant scientific literature, said: "Unfortunately, a great deal of misinformation about beavers and fish has been put into the public domain by those wishing to introduce beaver because of their lack of knowledge of the basics of salmon ecology and management. This has lead to a failure to appreciate the very significant differences between salmon in the Scottish landscape and climate and salmon in different situations elsewhere (even though this has been pointed out in the scientific literature). Nor have they shown any awareness of the very considerable experience that Scottish fisheries managers have of detecting and dealing with the impacts of the many types of artificial instream structures that restrict or stop salmonid spawning migrations and which is directly relevant to the instream structures built by beavers. These FAQs are aimed at dispelling this fog of misunderstanding and giving the Scottish public a clear appreciation of what it will mean to Scottish fisheries to have dams scattered across the headwater and tributary streams of Scotland in a way that it would simply not be permissible for humans to do".

View Tweed Foundation Paper of FAQs, Beavers and Fish. (PDF)







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