Chris White on Beavers in the wild

Minister for Rural Affairs, North Wales and Trefnydd (via email)

15 February 2022

Re: Releasing Beavers into the ‘Wild’: Environmental engineer or a waterway menace?

Dear Minister,

On behalf of CPWF on the 8 February one of our members (John Eardley) took part in the Welsh Beaver Project: Consultation Workshop at which Alicia Leow-Dyke (Welsh Beaver Project Officer with Wildlife Trusts Wales) outlined the benefits of releasing 10 pairs of Beavers into the Dyfi Valley saying that beavers had been absent since at least the 16th century.  Of course, over the intervening 400 years population density in the valley has increased, and changes in agricultural practices have seen rivers and streams managed.

Whilst beavers may bring some benefits to the overall ecology of rivers this should not be at the expense of migratory fish stocks particularly as in Wales these stocks are declared as either ‘At Risk’ or Probably at Risk’

Alicia’s presentation focused only on the positives including stating that beavers “only build dams on smaller tributary streams when the water is not deep enough for them to swim”, the wonderful benefits they bring to the hydrological cycle and the biodiversity of the catchment.  This statement ignores the fact that these smaller streams are the spawning and nursery grounds for migratory fish.  It should be noted that the NRW Executive and Board were told that the ‘All Wales Bylaws’, restricting angling methods, were necessary “in order that stocks can recover in the shortest possible time”. Introducing beavers on a river deemed to be ‘at risk’ for salmon or sea trout would be 100% counterproductive and fly in the face of the oft-quoted Precautionary Principle.  This would also make a mockery of the work at present being undertaken by Rivers Trusts on river restoration projects funded via the Salmon Action Fund or the Dee LIFE fund where barriers to migration are being removed.

There are claims by supporters of beaver re-introduction with respect to fisheries that:

“A wide range of evidence from Scandinavia and North America suggests that most beaver dams are passable to salmonids most of the time and that there is no clear evidence of a negative relationship between beaver activity and salmonids at a catchment level”.

And:   “Without appropriate management there could be negative effects on salmonid migration during dry autumns on smaller side streams with active beaver dams though this effect is likely to be highly site-specific based upon Scandinavian and North American”.

It should be noted that this is only a ‘suggestion’ there is no harm i.e. this is opinion and not based upon any evidence and in addition this opinion is based upon a catchment basis.  You cannot compare North American or Scandinavian River catchments with the much smaller Welsh river catchments where the negative impacts will be significant. 

It is noted in the final report of the River Otter Beaver Trial – ROBT (download link: The River Otter Beaver Trial | Devon Wildlife Trust) that the effect of beaver dams on migratory fish was given scant regard.  In the title of this letter, I have used the heading Environmental engineer or a waterway menace? from a paper by Dylan Roberts of the Game and Wildlife Conservation Trust ( )  which expresses caution on the release of beavers into the wild. 

Within the ROBT report the evidence from electrofishing above and below beaver dams clearly shows the marked decline in salmonid juveniles above beaver dams whilst claiming fish populations had increased, these were mainly minnows, brook lamprey etc. 

Photographs in the ROBT report to demonstrate that beaver dams do not obstruct upstream migration (in high flows) show sea trout leaping the dam which is then claimed that beaver dams are not a barrier to upstream migration.  Whilst adult migratory fish may be capable of negotiating beaver dams, juveniles cannot pass these on their downstream migration to the sea as there is no clear flow for them to follow i.e. water percolates through beaver dams.

It has been claimed in several papers that beavers improve fisheries as trout above beaver dams are larger (in one report it claims these are the fish anglers want to catch!), trout are predators so any juveniles dropping back into the impoundment caused by a beaver dam are rapidly eaten, which is why the trout are larger, this is short lived as there are no longer suitable spawning areas for these larger trout! 

It was interesting in the ROBT report that they identified the lack of/reduction in bullheads above beaver dams stating that this is due to bullheads requiring clean gravel and rifles to spawn, this also applies to migratory fish who need clean gravels.  There is a reference in the ROBT report to the requirement for further studies on the effect of beavers on fisheries.  The ROBT project was only funded for 5 years which ended in 2020. 

It should also be noted the need for ongoing maintenance due to beavers blocking culverts on drainage ditches resulting in unintentional flooding of fields, roads, and properties.  During the ROBT project this maintenance work was carried out by volunteers. The ongoing burden of damage caused by beavers will fall on riparian owners and local councils.  In Scotland the spread of beavers due to population growth is now causing issues and beavers are being trapped and relocated, I believe the 10 pairs proposed for the Dyfi valley will be from Scotland. 

There is a time and a place for the re-introduction of beavers but not at the expense of migratory fish, who at this present time are declared by NRW to be at severe risk.  The Precautionary Principle must be applied until the long-term effects on migratory fish stocks caused by beavers is fully understood. There must be a moratorium on the release of beavers into the wild on Welsh Rivers until such time as there is clear evidence that our stocks of salmon and sea trout are well on the road to recovery.


Chris White

Conservation Officer: Campaign for the protection of Welsh fisheries

CC via email:

Clare Pillman: CEO Natural Resources Wales

David Henshaw: Chairman – NRW Board

Ben Wilson: Principal fisheries officer NRW

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