Integrating molecular and traditional techniques to study the effects of beavers on migratory fish

摘要

Reintroduction of keystone species is considered part of the solution to restore
resilient freshwater ecosystems and stem the current biodiversity crisis. The
Eurasian beaver (Castor fiber) is one such species, shaping its habitat by felling
trees, building dams and creating wetlands which increase complexity and lateral
connectivity across a landscape. While the positive impacts on wider biodiversity
are well documented, the impacts on migratory fish are highly context dependent,
and require research across differing geographic scales. Finally, following
reintroductions, robust approaches to monitor species distributions are vital to
ensuring successful conservation translocations.
This thesis focuses on the integration of both molecular and traditional techniques
to monitor the impacts of beavers on migratory species across both the
catchment and local scale. Sequencing of environmental DNA (eDNA
metabarcoding) from water samples provided a cost-effective method to study
species distributions across large geographical scales. However, it is not possible
to monitor direct abundance or population demographics. Therefore, targeted
electrofishing approaches were applied on a local scale to monitor the impacts of
beaver engineering on migratory fish community composition, species densities
and individual fish condition. Finally, I integrated a published eDNA transport
model to investigate the influence of seasonal environmental variation on eDNA
transport distances.
Together, this research provides the first two empirical studies on beavers and
migratory fish from a British context. Furthermore, this thesis provided the first
utilisation of an eDNA transport model on beavers and represents a significant
enhancement in our understanding of the relationship between eDNA transport
and semi-aquatic mammals. Here, these findings reinforce the importance of
studying beaver impacts on migratory fish across contrasting geographical scales
and emphasise how molecular approaches can be tailored to the appropriate
environmental conditions depending on the goal of future monitoring.

奖励日期	13 8月 2026
源语言	English
奖励机构	University of the Highlands and Islands
导师	Bernd Hänfling (Supervisor)