Hardy, adaptable, and prolific, European green crabs (Carcinus maenas) are thought to have first arrived in North America in the 1800s in the ballast water of ships, and they have since been found at specific locations from Mexico to Alaska. They have a well-earned reputation as one of the most destructive marine invasive species in the world, with a plethora of direct and cascading impacts, both ecological and economic.
These efficient predators feed on a wide range of native species, from juvenile fish to other crustaceans, and they out-compete native crabs for food. They also can destroy eelgrass meadows and shellfish beds while feeding or burrowing for shelter.
For those whose lives intertwine with coastal ecosystems, the spread of green crabs is a growing concern, especially as the crabs continue to colonize new areas. To track and monitor their spread and create an early warning system, Hakai Institute researchers and their partners in the Integrated Coastal Observatory—a network of community partners that collectively samples marine waters from Puget Sound, Washington to British Columbia’s NorthCoast—are using a targeted genetic tool that isolates and detects any traces of environmental DNA (eDNA) from green crabs in a sample.
This genetic tool, quantitative polymerase chain reaction (qPCR), provides data on the amount of target DNA - green crab in this case - in a sample without the need for visual observation. What’s more, it allows for the detection of the green crab’s larvae, providing a mechanism to detect this invasive species before it claws its way into a new location and allowing for proactive actions to be taken to potentially slow expansion.
Partners
This research began as part of the Integrated Coastal Observatory (ICO). The ICO is a participatory science network run by the Hakai Institute that is composed of approximately 20 partner organizations in coastal BC, all using eDNA to monitor marine biodiversity.
Each of these partners is keen to incorporate leading-edge genetic approaches into their local stewardship initiatives. Through co-design and collaboration with these partners, it is clear that early detection and monitoring of green crab invasion is an area of critical interest to coastal communities. Our work in green crab detection is also expanding to additional regions and partnerships in coastal BC.
Timeframe
Our research using eDNA to monitor European green crabs began 2024 and leverages existing samples that have previously been collected as part of our genetic monitoring of coastal biodiversity. This is a growing area of research at the Hakai Institute that has evolved as a response to the rapid spread of this highly invasive species. We plan to carry out regular environmental screening for green crab well into the future, and ultimately our genetic data on green crab presence and relative abundance will be publicly available on the ICO webtool.
Context
The Biodiversity Genomics research group at the Hakai Institute is a leader in the use of Environmental DNA to monitor marine biodiversity, from plankton to invertebrates to fish to mammals. Based at the Quadra Island Ecological Observatory, this research group has a genomics facility designed specifically for processing environmental samples including dedicated genomics staff, clean rooms for eDNA, and DNA sequencers. Our expanding work using DNA to track invasive or endangered species is a logical extension of ongoing genetic monitoring on the BC coast.
Outcomes
Results of the project are forthcoming and will be publicly available in early 2026.
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