Environmental DNA (eDNA) detects the invasive rusty crayfish Orconectes rusticus at low abundances.

Area of Science:

• Aquatic ecology
• Invasive species management
• Molecular ecology

Background:

• Early detection of invasive species is crucial for cost-effective control.
• Traditional sampling methods struggle with low population densities characteristic of early invasions.
• Environmental DNA (eDNA) shows promise for sensitive detection but requires evaluation across diverse taxa and habitats.

Purpose of the Study:

• To assess the efficacy of eDNA for detecting the invasive rusty crayfish (Orconectes rusticus).
• To evaluate eDNA's ability to reflect rusty crayfish relative abundance in inland lakes.
• To develop a protocol for eDNA monitoring of crayfish invasions.

Main Methods:

• Paired conventional baited trapping with water sampling for eDNA analysis using qPCR.
• Modeled eDNA detection probability using relative abundance and site characteristics.
• Assessed the relationship between eDNA copy number and crayfish relative abundance.

Main Results:

• eDNA detected rusty crayfish in all lakes with trapped individuals, including those with zero trap catch.
• Detection probability of eDNA was accurately predicted by crayfish abundance and lake water clarity.
• A weak correlation was observed between eDNA copy number and estimated crayfish relative abundance.

Conclusions:

• eDNA is a sensitive tool for detecting invasive rusty crayfish, even at low densities.
• The developed eDNA protocol and statistical models can guide sampling efforts for invasive crayfish surveillance.
• Recommends incorporating eDNA into monitoring programs for invasive or imperiled crayfishes and other benthic arthropods.