Nonlinear relationship between Silver Carp density and their eDNA concentration in a large river.

David P Coulter,James E Garvey,Ping Wang,Alison A Coulter,Jessica J Eichmiller,Peter W Sorensen,Grace E Van Susteren,Matthew Lauretta

doi:10.1371/journal.pone.0218823

Abstract

Although environmental DNA (eDNA) is increasingly being used to survey for the presence of rare and/or invasive fishes in aquatic systems, the utility of this technique has been limited by a poor understanding of whether and how eDNA concentrations relate to fish density, especially in rivers. We conducted a field study to systematically test whether the eDNA released by a model invasive fish, Silver Carp (Hypophthalmichthys molitrix), was related to the density of this species in a large river. We quantified fish density throughout the 460 km long Illinois River using hydroacoustic surveys at 23 sites while concurrently collecting 192 surface water samples for eDNA analysis. We found that Silver Carp numerical density and biomass density were positively and non-linearly related to eDNA concentration and detection rate. Both eDNA concentration (copy number) and detection rate increased rapidly as Silver Carp density increased but plateaued at moderate densities. These relationships could prove useful for estimating Silver Carp relative abundance in newly invaded locations where population numbers are low to moderate. Future studies should explore the causes of this nonlinear relationship as it would ultimately benefit aquatic species monitoring and management programs.

Highlights

The ability to efficiently determine the presence of rare and/or invasive fishes and assess either their abundance or biomass is requisite to developing management strategies for these species [1]
This study, one of only a few to quantify the relationship between the density of a fish and its environmental DNA (eDNA) concentration in a large river, identifies a significant nonlinear relationship between Silver Carp density and the eDNA they release in the Illinois River
These results indicate that quantification of eDNA concentration is a promising tool for population assessments and management programs in rivers for this important invasive species, and perhaps others, especially at low densities in newly invaded areas

Summary

Introduction

The ability to efficiently determine the presence of rare and/or invasive fishes and assess either their abundance or biomass is requisite to developing management strategies for these species [1]. Reliance on traditional capture gears can be time-consuming, expensive, produce biases toward certain species or habitats, and may at times be ineffective [1,2,3,4]. These gears may cause stress, injury, or mortalities [5]. The funders provided support in the form of salaries for authors [DPC, PW, AAC, GEV, JJE, PWS], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. Fisher Scientific Inc. had no official collaboration with this study, did not influence study design, data collection and analysis, decision to publish, or preparation of the manuscript

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Conclusion