The Common Shore Crab (carcinus maenas) as an invasive Species

Native to Atlantic Europe, the western Baltic and west Africa to Mauritania, Carcinus maenas is arguably one of the worst invasive marine species in the world. They are introduced to new environments mainly by ship ballast water and hull fouling but many other vectors can contribute. This crab is an omnivore which means it can eat plants, animals, and protists which make it very well suited for a wide range of habitats. The shore crabs carapace width can range from 1-2 cm to 9-10 cm and it can range in color including shades of green, brown, and red. On the east coast of North America it can live up to 6 years but on the west coast and in its native environment males can live up to 5 years and females 4 years. This species introduction to new environments has always been accidental and was first introduced to the North American east coast in the 1800s but spread to the west coast via seaweed and other means by the 1900s.  (, 2017)

Carcinus maenas has environmental and economic impacts due to its resilient nature. Just one of these crabs can consume up to 40 half inch clams in one day and in the 1950s was the cause of a New England shellfish companies end. It has been estimated that it can cause up to $22.6 million on predation alone which could eventually disrupt present business for people who depend on this crabs prey to live. (, 2017) This organism has major impacts on the environments it invades. Due to its omnivorous nature and resilience, it can cause huge changes in habitats. It feeds on species of at least 104 families, 158 genera, 5 plants and protists, and 14 animal phyla. This can cause a decrease in abundance of species native to a given environment and possibly extinction. (, 2017)

Once an invasive species has been introduced to a new environment and thrives it is nearly impossible to reverse. Eradication and other means of intervention have been attempted on the Carcinus maenus but to no avail. It is just one of many invasive species that can only serve as a lesson for the future.

Related links: (2017). Carcinus maenas (European shore crab). [online] Available at: [Accessed 13 Feb. 2017].



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