eDNA is a useful tool for early detection of invasive species of green crab

European green crab found in Willapa Bay, Washington in 2016. Credit: P.Shaun MacDonald / University of Washington

European green crabs eat shellfish, dig holes in mud, destroy swamp habitats, and destroy precious seagrass beds. Invasive species also breed rapidly, making it a nightmare for wildlife managers seeking to control their spread in Washington’s seawater.

Last month, Governor Jay Inslee issued an emergency order in response to more than 70,000 people. crab In recent years, crab populations have increased dramatically on the outer coasts of Washington and elsewhere in Puget Sound, captured on land in Nation.

As the invasion of green crabs in the state worsens, new analytical methods developed by scientists at the University of Washington and Washington Sea Grant contain future invasions, water With testing Genetic analysis..Results were published online in the journal on February 6th. Ecological applicationWe show that DNA-based technology works equally well to detect the presence of green crabs as a trap for catching live animals. This is a more painstaking process. The results suggest that these two methods may complement each other as an approach to learning where the range of species is expanding.

The new method depends on Genetic material In an environment known as eDNA found in water after the passage of an organism.Scientists can collect bottles of water from positionExtracts DNA from water and identifies species that have recently existed in the area.

“The resources to address this issue are limited. It is important to think of ways to allocate these resources efficiently and effectively,” said the first master’s degree student at the School of Marine Science and Technology, University of Washington. The author, Abigail Keller, states. Environment issues. “It’s important to know the best situation for detecting an invasive species of green crab using eDNA, and that’s what our research has done.”

Credit: University of Washington

The research team relied on data collected over a three-month period in 2020 from 20 green crab traps in Puget Sound and the outer coast. Captures at these locations include multiple tribes, the Washington Sea Fish and Wildlife Service, which is the leader in crab management in Washington, the Washington Sea Grant crab team, and other state and federal agencies.

In this study, researchers visited each location to collect water samples and then performed genetic analysis to detect both the presence and quantity of the European green crab at each location. In this way, they were able to validate the eDNA data with the presence and number of actual crabs. They found that using eDNA to detect species presence and abundance was as sensitive as capturing and counting live crabs.

Researchers say this is important because eDNA as a detection method is new and the method of interpreting eDNA detection in past scenarios is not always clear. This study shows how traditional monitoring methods (in this case crab capture and counting) can be combined with eDNA technology to more effectively detect and control the development of invasive species.

“This is a very well-tested example of how to use eDNA in the real world. It’s really exciting to me,” said Ryan Kelly, an associate professor of marine environmental issues at the University of Washington. I am. “A lot Invasive species, And because of the many endangered and endangered species that are difficult to monitor, this is one of the key advances in all of these aspects. “

This study also assesses when eDNA adds value to the monitoring of invading crabs, and when conventional capture and counting still make the most sense. for example, Water sample Testing the DNA of green crabs in remote areas or in areas where the outbreak has not yet been identified can save time and resources at the expense of deploying traps. Alternatively, researchers explained that eDNA would probably be useless where a large number of green crabs are already inhabited and community scientists and managers have already captured and managed their populations. ..

eDNA is a useful tool for early detection of invasive species of green crab

European green crab caught at Lagoon Point, Washington (Whidby Island) in 2018. Credit: Emily Grason / Washington Sea Grant

“From an administrative point of view, the value of this tool really comes to life in more remote areas and where there are many coastlines to cover, such as Alaska, where green crabs have not yet been detected,” co-authors said. Emily says. Grayson, a marine ecologist who leads the Washington Sea Grant club team. “I see eDNA as another tool in the toolkit, and I can imagine scenarios that can be used with traps, especially as an early detection method.”

Finding these crabs immediately after occupying a new location is important for controlling populations and protecting native habitats. Administrators can anticipate new invasions by testing water from multiple locations, followed by further water testing, ground monitoring, and trapping if green crab DNA is detected. increase.

This paper identified the DNA of a green crab in one place near Vashon Island where the species has not yet been captured. A year later, the research team conducted intensive captures and retested the water. No DNA was found for green crabs or additional green crabs. Researchers believe that the previous positive sample was likely to have picked up larvae of green crabs that were not present at the location a year later. In particular, this effort represents an important test case of how eDNA and traditional trapping can be implemented together for the management of green crabs.

“The reason we first pursued this project is that early detection of crabs is difficult. It’s like finding a needle in a haystack,” said Associate Professor of Environmental Studies and Aquatic at the University of Washington. P. Sean McDonald said. UW Principal Investigator for Fisheries Science and Crab Team Research. “Therefore, if we can detect those needles by adding eDNA to the toolkit, it’s a great thing we have at our disposal.”

Invasive species of green crab found near Sequim, Washington

For more information:
Abigail G. Keller et al, Tracking Fronts of Invasion by Environmental DNA, Ecological application (2022). DOI: 10.1002 / eap.2561

Quote: EDNA is an intrusive green crab (February 16, 2022) obtained from https: // on February 16, 2022. ) Is a useful tool for early detection.

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eDNA is a useful tool for early detection of invasive species of green crab

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