Quantification of eDNA shedding rates from invasive bighead carp Hypophthalmichthys nobilis and silver carp Hypophthalmichthys molitrix

• Published in: Biological conservation 2015-03, Vol.183, p.77-84
• Main Authors: Klymus, Katy E., Richter, Catherine A., Chapman, Duane C., Paukert, Craig
• Format: Article
• Language: English
• Subjects: Asian carp; Biomass; Carp; Conservation; Density; eDNA; Fish; Hypophthalmichthys molitrix; Hypophthalmichthys nobilis; Invasive species; qPCR; Shedding; Sheds; Species detection; Spreads; Water temperature
• ISSN: 0006-3207; 1873-2917
• DOI: 10.1016/j.biocon.2014.11.020

•We examined potential factors influencing eDNA shedding rates of two invasive fish.•We show that the amount of eDNA shed is positively related to fish biomass.•Water temperature did not affect the amount of eDNA shed, but feeding and diet had an effect.•Identification of PCR inhibited samples is important for eDNA monitoring programs. Wildlife managers can more easily mitigate the effects of invasive species if action takes place before a population becomes established. Such early detection requires sensitive survey tools that can detect low numbers of individuals. Due to their high sensitivity, environmental DNA (eDNA) surveys hold promise as an early detection method for aquatic invasive species. Quantification of eDNA amounts may also provide data on species abundance and timing of an organism’s presence, allowing managers to successfully combat the spread of ecologically damaging species. To better understand the link between eDNA and an organism’s presence, it is crucial to know how eDNA is shed into the environment. Our study used quantitative PCR (qPCR) and controlled laboratory experiments to measure the amount of eDNA that two species of invasive bigheaded carps (Hypophthalmichthys nobilis and Hypophthalmichthysmolitrix) shed into the water. We first measured how much eDNA a single fish sheds and the variability of these measurements. Then, in a series of manipulative lab experiments, we studied how temperature, biomass (grams of fish), and diet affect the shedding rate of eDNA by these fish. We found that eDNA amounts exhibit a positive relationship with fish biomass, and that feeding could increase the amount of eDNA shed by ten-fold, whereas water temperature did not have an effect. Our results demonstrate that quantification of eDNA may be useful for predicting carp density, as well as densities of other rare or invasive species.