You know all those articles we have been reading about how the anglers hate beavers coming back to Scotland because they’ll ruin things for all the salmon? (By which they mean trout?) Well get ready to watch some Scottish fishermen sputter.

The response of a brown trout (Salmo trutta) population to reintroduced Eurasian beaver (Castor fiber) habitat modification

This study investigated the response of a population of brown trout (Salmo trutta) to reintroduced Eurasian beaver (Castor fiber) habitat modifications in northern Scotland. The field site comprised two streams entering a common loch; one modified by beavers, the other unaltered. Electrofishing and PIT telemetry surveys indicated abundance of post-young-of-the-year (post-YOY) trout was higher in the modified stream. Considering juvenile year groups (YOY and post-YOY) combined, abundance and density varied with year and season. In the modified stream, fork length and mass were greater, there was a greater variety of age classes, and mean growth was positive during all seasons. Beavers had profound effects on the local brown trout population that promoted higher abundances of larger size classes. This study provides important insight into the possible future effect of beavers on freshwater ecosystems.

More fish and bigger fish. Wow will you look at that. I’d be surprised if every single study in every single place hadn’t already proven the same thing. Do we think the Scotish Anglers will listen?

This study provides evidence that local-scale modification of river habitat by Eurasian beavers can benefit brown trout populations by enhancing the heterogeneity and suitability of habitat for a range of life stages, thus improving abundance and growth, a useful proxy for fitness. Based on previous reviews on the subject (e.g., Kemp et al. 2012), this finding is not unexpected, although it does provide useful confirmation that relationships observed elsewhere appear to hold true for upland areas of northern and western Great Britain. The results may provide helpful information to riparian landowners and policy makers in relation to the management of expanding Eurasian beaver populations in European rivers which host commercially important and sensitive salmonid populations.

These findings may go some way to reassure representatives of fisheries interests that, from the perspective of brown trout habitat suitability at least, the presence of beaver may provide a cost-effective and self-sustaining means to maintain and restore the ecological status of upland rivers without threatening native fish populations. Nevertheless, there remains a need to further explore the impact of beaver activity at a catchment scale, and the impact of dams on the movement of multiple species of fish, including the migratory salmonid life stages.

I am shocked. Shocked I tell you to learn that having more little bugs to eat in safe unfrozen deep water leads to more and bigger salmon even when those nasty rodents are involved,

I think I heard ever Scottish angler say that at the same time.