Determining the ability of two approaches to measure environmental DNA (eDNA) to reliably quantify the abundance of invasive common carp in Minnesota lakes

Project manager: Peter Sorensen

We will develop and test the ability of eDNA to estimate the abundance of common carp in Minnesota lakes. This study will complement the eDNA study of Asian carps which focuses on presence/absence measures of a rare AIS. Here, we use the common carp as a model because it is extremely abundant, well understood, and the subject of management efforts.

The primary objective will be to determine if we can accurately and reliably measure the abundance of common carp in waters they are known to inhabit. We will develop and validate two techniques: quantitative PCR (qPCR) of carp mitochondria (conventional eDNA analysis) and qPCR of microbial rDNA from carp feces combined with sequencing (also known as metagenomics). Metagenomics is promising because it could offer greater sensitivity and more information on species abundance and ecosystem health. Initial efforts will identify molecular markers for common carp by comparing mitochondrial sequences from the common carp and close relatives. Quantitative PCR assays will then be developed.

In a second step, the effects of key environmental variables on the abundance of these markers will be examined in laboratory mesocosms. Lastly, we will apply the most promising technique(s) to study the relationship between the abundance of these markers and the abundance of common carp in local lakes.

Project start date: 2012

Estimated project end date: 2016, Phase 2 to continue through 2018

Updates and progress:

Phase II: Attracting carp so their presence can be accurately assessed

Project manager: Peter Sorensen

Description: MAISRC researchers are currently working to prevent adult bigheaded (Asian) carp form migrating upstream from the lower Mississippi River using acoustic deterrents and modifying gate operations. Because this needs to be very strategic and efficient, MAISRC must have extremely accurate information on the abundance of adult invasive carp in the area.

This project aims to remedy the deficiencies currently associated with eDNA by developing new techniques to cause predictable aggregations of adult invasive carps. This will facilitate their accurate measurement using eDNA and pheromones or alternately their being trapped and removed.

This research will examine the possibility of causing aggregations using both sexual and feeding cues.

In order to develop reliable and practical ways of using sexual stimuli to find carp, researchers will artificially induce female sexual behavior and sex pheromone release using hormone implants. They will then determine if they can track these aggregations using eDNA measurements and sex pheromone concentrations. They will also test the possibility that a Judas fish (a sterilized fish equipped with a tracking device) could be used both to drive an aggregation and/or track it. Additionally, researchers will test whether food or a synthesized compound could drive aggregations of carp.

Project start date: 2015

Estimated project end date: 2018

Updates and progress:
Following data collection in 2015, it was found that food was able to drive large aggregations of common carp which we successfully measured using eDNA and pheromones. This baiting scheme has now been perfected and in some cases, a third of the population of mature common carp were able to be attracted using food, all while measuring abundance with a new level of sensitivity, precision, and accuracy. Pheromone-releasing Judas fish were also evaluated for their ability to attract other carp. This research has now informed a pilot study of attracting Silver carp in Illinois using both methods.