The Chinese mitten crab (scientific name Eriocheir sinensis) is a species of crab native to the coastal rivers and estuaries of East Asia, specifically ranging from the Bohai Sea and the southern coast of South Korea down to Macau, near Hong Kong. While indigenous to this region, it has gained notoriety globally as a significant invasive species. This crab has successfully established populations across Europe and North America, likely introduced through mechanisms such as ballast water in ships. The species is recognized by the World Conservation Union (IUCN) as one of the “100 worst invasive species” due to its widespread ecological and economic impacts.
Primary Food Sources
Chinese mitten crabs exhibit an opportunistic and omnivorous diet, consuming a wide array of food items depending on availability and their life stage. Their diet includes both plant and animal matter, showcasing their adaptability to various aquatic environments. This broad dietary range contributes to their success as an invasive species, allowing them to thrive in diverse habitats.
They consume algae, various aquatic plants, and detritus, which is decaying organic material. They also feed on macroalgae, which are larger forms of algae.
Their animal-based diet consists of small invertebrates such as worms, insect larvae, snails, and mussels. They also prey on small crustaceans and fish eggs. Larger individuals may consume smaller fish or other crab species.
Feeding Strategies
Chinese mitten crabs employ various feeding strategies to acquire their diverse diet, adapting their methods based on their size, life stage, and the food sources present in their environment. These strategies allow them to efficiently exploit available resources.
Smaller or juvenile crabs use filter feeding. They use specialized bristles, known as setae, located on their claws (chelae) to strain plankton and other small organic particles from the water column.
Crabs are effective scavengers, readily consuming dead or decaying organic matter found on the riverbed or estuary floor. They also actively hunt and consume live prey, using their strong claws to capture and manipulate small invertebrates and fish. Their feeding behaviors are adaptable, shifting in response to the abundance of different food types and as the crabs grow and mature.
Ecological Consequences of Their Diet
The broad and adaptable diet of Chinese mitten crabs has significant ecological consequences, particularly in regions where they are an invasive species. Their feeding habits can disrupt native ecosystems and alter the balance of local populations.
Their consumption of native species, including macroalgae, invertebrates, and fish, can lead to substantial declines in these populations. This competition for food resources can displace native species, reducing their numbers and potentially impacting the entire food web. Such impacts can alter the structure of benthic communities, which are organisms living at the bottom of aquatic environments.
Furthermore, the feeding activities of Chinese mitten crabs can contribute to habitat degradation. Their burrowing activities, often undertaken to seek food or shelter near food sources, can damage riverbanks and infrastructure like levees. This burrowing can increase erosion and instability of banks. The cumulative effect of their diet and associated behaviors can lead to changes in biodiversity and the overall health of invaded ecosystems.