The Asian Shore Crab: a new marine pest

Port Phillip Bay has hosted more than 160 invasive marine species since colonisation started. But only recently we have discovered a brand new one. The Asian Shore Crab (Hemigrapsus sanguineus) was discovered in 2020 and is here to stay.

The Asian Shore Crab: a new marine pest

The crab is native to the western Pacific, and was first observed as a marine pest in North America in the late 1980s, where it has taken over large areas of the east coast. Like many other invasive species, it was most probably introduced in Port Phillip Bay through ballast water from shipping vessels.

The Asian Shore Crab is a small, aggressive crab that can grow up to 5cm in width. It has a distinctive, square-shaped carapace, banded legs and dark spots on the claws. The crab is highly adaptable, and is able to survive in a wide range of habitats, including rocky shores, sandy beaches, and tidal creeks. You can imagine why the Bay makes the perfect habitat!

The introduction of the Asian Shore Crab has the potential to have significant ecological impacts. It is a generalist feeder and a highly effective predator, and will eat a wide variety of prey, including other – native – crabs, small fish, and molluscs. Its ability to outcompete and displace native species can have a knock-on effect on the wider ecosystem, with potential consequences for biodiversity, food webs, and ecosystem functioning.

Yikes! What now?

In order to effectively manage invasive species, it is important to adopt a multi-pronged approach that includes prevention, early detection, and rapid response, as well as ongoing monitoring and research to better understand their ecology and impacts.

However, once a marine pest is ‘established’ in a new location, there is no getting rid of them. Any attempt to eradication needs to then shift to a management approach: this includes limiting further incursions of crabs by controlling ballast water, monitoring and surveillance programs to track their distribution and abundance, and potentially the use of physical control methods to reduce their impact.


EcoCentre’s PestWatch! project, funded by the Port Phillip Bay Fund, aims to take action on marine pests. Over the next year and a half, our Community Rapid Response Teams, made up of community volunteers, will be trained in the identification of the Asian Shore Crab, and scour the beaches of the Bay in search of them. We will record their numbers and locations, which will hopefully give us insight into their preferred habitat and how far they have spread. Results will be shared with the Biosecurity team of the Department of Energy, Environment and Climate Action.

If you want to learn more about this critter and get on board, join us for our free PestWatch! webinar on Thursday 23 February at 6:30 pm. REGISTER HERE

This project is funded by the Port Phillip Bay Fund.
Article written by the Port Phillip EcoCentre resident marine biologist, Fam Charko.

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The EcoCentre acknowledges the Kulin Nations, including the Yalukit Willam clan of the Boon Wurrung language group, traditional custodians of the land on which we are located.

We pay respects to their Elders past and present, and extend that respect to other First Nations and Elder members of our multicultural community.