Genetic characteristics of coastal cutthroat trout inhabiting an urban watershed
Watersheds in urban areas are often heavily degraded due to human activity, which can have negative impacts on freshwater fishes. Monitoring the genetic characteristics of urban populations can provide insights into the impact of development on aquatic ecosystems. We performed a genetic analysis of coastal cutthroat trout (Oncorhynchus clarkii clarkii) inhabiting urban tributaries in Portland, OR. By analyzing nuclear microsatellite genotypes, we were able to assess population structure, genetic diversity, and effective population size for six locations across two tributaries on opposite sides of the Willamette River. Genetic diversity was generally equivalent across all sampling locations, although populations from smaller tributaries higher in the stream network had lower levels. Levels of effective population size were low but within expected ranges for small salmonid populations. As anticipated, smaller populations had higher levels of inter-individual relatedness. The primary genetic structure divided populations on opposite sides of the Willamette River, although there was evidence of dispersal between the two groups. Our results suggest that cutthroat trout inhabiting metropolitan areas are not necessarily genetically impoverished and may exhibit characteristics typical of populations in more ‘natural’ environments. Understanding how fish, especially anadromous species, respond to urban environments is essential to evaluating the value of these areas for conservation planning.
KeywordsOncorhynchus clarkia Dispersal Urban ecology Metapopulation Population genetics
We thank J. Von Bargen and M. Brinkmeyer (USFWS) for processing samples in the lab. Personnel from the Columbia River Fish and Wildlife Conservation Office collected tissue samples in the field. We thank R. Twibell (USFWS) and personnel from the Columbia River Fish and Wildlife Conservation Office for comments that improved the manuscript. We declare no conflict of interest in the publication of this study. We thank editor David Noakes and two peer-reviewers for their constructive comments. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the US Fish and Wildlife Service.
Funding was provided by the City of Portland’s Bureau of Environmental Services and the U.S. Fish and Wildlife Service’s Columbia River Fish and Wildlife Conservation Office. Collection of trout for this study was conducted with permits and animal use approval required by the US Fish and Wildlife Service and City of Portland Bureau of Environmental Services.
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