Derek Gow has pointed out to me that the value of the return of the sea eagle to Mull is reckoned to be £1.8 million annually at the present time so it is likely that this is an underestimate.
All the same Roger's comparison is absurd, it seems to me, because it compares an established 'industry' with something that is largely hypothetical.
Why make this comparison at all unless you think that beavers are somehow going to destroy, or seriously affect the salmon fisheries, which is the Tweed Foundation's line.
In its campaign to prevent or promote antagonism to the trial release of beavers in Argyll, the Tweed Foundation has given publicity to the report (http://atlanticsalmonfederation.org/pei/2009peireport.html) from Prince Edward Island in Canada that attributes decline in catches of salmon to the presence of beaver dams.
Daryl Guignion, who wrote the report for the Prince Edward Island Atlantic Salmon Foundation stated only a few months before this was published in March this year that 'the biggest threats to salmon on P.E.I. are sediment and runoff coming from farmers fields and highways, and rivers blocked by bridges and culverts that prevent salmon from moving upstream.' (CBC news 11 August 08).
A Google search (CBC news Daryl Guignion salmon as key words) suggests that there is a long history of problems with the rivers of Prince Edward Island. These have much to do with misuse of the land as mentioned by Professor Guignion and rather little to do with beavers.