About This Project

Nanophyetus salmincola and Ceratomyxa shasta, two parasites of freshwater species, have been associated with significant mortality in juvenile salmon, as well as severe disease in wildlife, domestic animals, and even humans. Dam construction by beavers has been shown to increase biodiversity (variety of species in a system), which, in turn, has been shown to reduce parasites. Here, we will investigate whether beaver dams may provide natural control of these parasites in wildlife species.

Ask the Scientists

What is the context of this research?

Ecosystem engineers are species that physically modify their habitat. These animals play a significant role in shaping habitat heterogeneity (range of habitats) within their ecosystem. One well-known ecosystem engineer, the beaver (Castor canadensis), drastically alters its environment by damming freshwater streams and rivers. These changes result in increased diversity of habitats available for other species.4,8^,9As such, beaver-modified habitats are associated with an increase in biodiversity of both aquatic and terrestrial species.4,9^,10 However, while the association between beaver dams and increased biodiversity of macroscopic species has been uncovered, little is understood about the impacts of beaver dams for parasite species that may also share their ecosystems.

What is the significance of this project?

Parasites transmitted by aquatic animals pose significant threats to important fish species; mammals and birds of critical conservation status; and humans and domestic animals.3^,7^,10 In salmon, the parasites Nanophyetus salmincola and Ceratomyxa shasta have been associated with significant mortality and are particularly difficult to treat due to lack of handling success. In the face of these challenges, beaver-modified environments may provide a natural intervention method for parasitic control. The Dilution Effect is an emerging hypothesis that suggests that more biodiverse ecosystems have lower levels of parasitic transmission.1^,5 Here, we will evaluate how beaver dams, and the ensuing biodiversity they create, influence parasite diversity and abundance within freshwater ecosystems.

What are the goals of the project?

Our study will evaluate the impacts of beaver dams on parasite diversity by investigating the following:

1) Is the diversity of vertebrate and invertebrate species different in areas with beaver dams?

2) Is parasite diversity different in areas with beaver dams?

3) What is the relationship between overall macro species diversity and parasite diversity in areas with and without beaver dams?

This study will utilize existing infrastructure from ongoing studies in the Crooked and John Day River, Oregon (PIs Orr and Petersen) to investigate how beaver dam analogs (treatments) and pristine environment (controls) differ in terms of environment, hydrology, and representative species (both parasites and macro-) above and below replicate plots.

For full details of our methods see the “Methods” section.