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USGS - science for a changing world


Christopher M Merkes


Upper Midwest Environmental Sciences Center

Office Phone: 608-781-6316
ORCID: 0000-0001-8191-627X

Supervisor: Jon J Amberg
Description of Work This spring (2014) we will measure Asian carp eDNA over time at a Missouri River site downstream of multiple spawning areas before and during spawning. We will measure the amount of Asian carp eDNA in water samples. The amount of eDNA will be related to the numbers of eggs and larvae counted in matched samples (water samples taken at the same time and place). The time since the eDNA was released by the carp will be estimated and these results will be related to the average age of AC eggs and larvae in matched samples. We will also test for substances which interfere with the eDNA measurement techniques and can lead to false negatives. We will also be validating markers developed by USGS and...
Invasive species may vary in their seasonal distribution and abundance due to environmental conditions such as precipitation and temperature. Bigheaded carps, which include silver and bighead carp, are one such taxon of invasive species that appear to change habitats seasonally. Seasonal changes in bigheaded carp distribution may occur because of hydrological changes, water temperature changes, and spawning activities. Monitoring this seasonal dispersal and migration is important for management to control the population size and spread of the species. We examined if environmental DNA (eDNA) approaches could detect seasonal changes in the occurrence of DNA in water samples and used these approaches to calculate the...
This data set was collected to provide examples and aid in developing a standardized way of determining LOD and LOQ for eDNA assays and has 3 data files. GEDWG_LOD_DATA3.csv is raw qPCR data from multiple labs running multiple standards of known concentration for eDNA assays they regularly use. Comparison-Data.csv is the merged data output from running a generic LOD/LOQ calculator script multiple times with different LOD model settings. The generic LOD/LOQ calculator script is available at:, and details about the multiple settings used are commented in the analysis script available at:
This dataset includes information from ichthyoplankton sampling for silver carp and bighead carp collected from three main reaches in the Upper Mississippi River Basin, including the La Grange, Peoria, Starved Rock, and Marseilles reaches of the Illinois River, Pool 20 of Mississippi River, and the St. Croix River. Data include the number of bigheaded carp eggs and larvae identified using traditional manual sorting techniques, and genetic data derived from quantitative PCR (qPCR) and 4 bigheaded carp markers (SCTM4/5 and BHTM1/2) that were used to identify the amount of DNA in ichthyoplankton tow samples. These data provide information for natural resource agencies and managers who could use this qPCR screening...
This script is designed to analyze qPCR data for many replicates of known concentration DNA standards and determine the limit of detection (LoD) and limit of quantification (LoQ) for use in environmental DNA applications. It is written in the hopes that users with even limited knowledge of R will be able to successfully use the code to analyze their own data in the same way as other eDNA researchers to get similar results and automatically generate plots to visualize the data. The code has 5 lines for user input and requires a few simple restrictions on the input data, but after that the user should be able to run the code without any further coding or interventions. No R programming ability is required to run this...
Categories: Data
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