Non-native aquatic plants can have far reaching and unforeseen impacts on habitat for fish, invertebrates, and other wildlife; however, logistical constraints often don’t allow for investigation of impact across multiple trophic or community levels. The lack of comprehensive information regarding impact of non-native plants on aquatic ecosystems can hinder managers’ ability to prioritize management resources. The Chehalis River is an excellent system to investigate some of these dynamics as is it home to a diverse community of economically and culturally important fish species; like many rivers and lakes in Washington, it is also home to several non-native aquatic plants, namely non-native parrotfeather (Myriophyllum aquaticum) and Brazilian elodea (Egeria densa).


Aquatic plants – like non-native parrotfeather shown here – can dramatically alter physical and chemical characteristics of fish habitats

The Chehalis River Basin also encompasses a majority of the distribution of Olympic mudminnow (Novumbra hubbsi), Washington State’s only endemic fish species; Olympic mudminnow also have the dubious distinction of having the smallest range of any mudminnow species in the world. Listed as ‘Sensitive’ by Washington State Department of Fish and Wildlife in 1999, there is nonetheless a very sparse understanding of population sizes and environmental drivers of habitat suitability and occupancy for this species. Without this information, it is difficult to design effective management plans for long term sustainability and conservation.

With funding from the Washington State Department of Ecology, in 2013 we initiated a field-based project to measure the ecological impacts of non-native parrotfeather on fish habitats in the Chehalis River. Over two years we comprehensively sampled 22 sites on the Chehalis River, measuring plant, invertebrate and fish communities as well as water quality in response to invasion by parrotfeather. These sites were also selected based on suitability for occupancy by Olympic mudminnow, which we chose as a focal fish species.

Products from this project include a review article focused on the ecology and conservation of the five species of mudminnow worldwide and a research article describing the environmental drivers of occupancy and detection of Olympic mudminnow on the Chehalis River (article in press). A third article (in preparation) will focus on the ecological impacts of non-native parrotfeather on fish habitats across multiple community levels.

We are continuing our research in the basin with sampling in 2015 and 2016; this sampling will focus on describing the extent and distribution of non-native parrotfeather in riverine and adjacent habitats of the Chehalis River. The distribution and spread of parrotfeather is being investigated in multiple years in relation to local and landscape scale drivers of presence and persistence. We are also working with project partners to test the efficacy of management and control options in context of these environmental drivers.


Like other mudminnow species, Olympic mudminnow are decided habitat specialists, preferring shallow and densely vegetated wetlands

As a whole, our work in the Chehalis River is intended to advance the science-based management and conservation of Olympic mudminnow, while also furthering our understanding of the impacts of non-native aquatic plants on sensitive fish habitats.

Project Goal Statement: To evaluate the ecological impacts of non-native aquatic plants on fish habitat in the Chehalis River, as well as establish the current distribution and projected spread of parrotfeather in the Chehalis River Basin. The goals related to Olympic mudminnow are to identify new riverine populations along the Chehalis River, investigate the environmental drivers of occupancy and detection, and guide development of standardized sampling and monitoring protocols for this highly endemic species.

Project timeline: June 2013 – June 2017

Project partners and related links:
Washington State Department of Ecology
Washington State Department of Fish and Wildlife
Washington State Department of Natural Resources
Thurston County Noxious Weed Department


Review article in FisheriesEcology and conservation of mudminnow worldwide” and related blog post

Research article in Transactions of the American Fisheries Society “Environmental drivers of occupancy and detection of Olympic mudminnow”

Poster presented at the Meeting the Challenge conference on impacts of non-native parrotfeather