Our treasure of the month: The Chinese Mitten Crab
Among all animals, it is one of the 100 most dangerous invaders worldwide. For research at LIB, on the other hand, the Chinese mitten crab from 1924 is a great collection treasure. Eriocheir sinensis is a clear example of how humans are altering the distribution of species, affecting the condition of native ecosystems worldwide.
The name of the Chinese mitten crab comes from its hairy claws, which look like woolen gloves. The crab is native to the river and estuarine areas of north and southeast China and Korea, but has also been found in Germany for almost 100 years. It was probably once introduced with ballast water from ships.
The first record of this species in Germany dates back to 1912 from the Aller River near the town of Rethem (Lower Saxony). Two years later, the hairy crab was first recorded in the Elbe River. In the 1920s and 1930s, it spread rapidly throughout northern Europe, especially in the estuaries of the western Baltic Sea and the North Sea, but also inland, for example in the Czech Republic and more than 700 kilometers up the Elbe beyond Hamburg.
One of the first researchers to study this invasive species was Dr. Albert Panning, who was curator of the Crustacea collection at the Zoological Museum in Hamburg from 1920 to 1957. The scientist focused on documenting and analyzing the extent and manner in which this species spread. For example, he studied dispersal strategies important to the transport of swimming larvae and the migrations of juveniles living in estuaries.
Thanks to Panning’s work, the Crustacea collection at LIB Hamburg contains some of the first specimens found in Germany in 1924. The most recent specimens in the scientific collection were collected just a few days ago by local fishermen in the Elbe River. In total, more than 150 specimens of the mitten crab are preserved in the Hamburg collection.
“It is very important for our research to collect specimens of the mitten crab over decades, or now over a century,” emphasizes Dr. Nancy Mercado Salas, head of the Crustacea section at the Leibniz Institute for Biodiversity Change Analysis (LIB), Hamburg. “Many small changes can only be studied thanks to the Natural History Collections, as in the case of the mitten crab: using these collection objects and the information associated with them (e.g., date, location, water characteristics), we have been able to study in detail how these animals have spread in Germany and what environmental factors are important for their survival and establishment. We can also analyze how populations have changed over the years, e.g., adults from the 1920s are larger than those collected in recent years. We’re also looking at genetic variation between different geographic populations – that is, whether and how it’s changing.”
The Chinese crab poses a significant threat to local ecosystems and native wildlife by severely displacing native species. It has been calculated that these hairy crabs have caused financial damage of more than 80 million euros since their arrival in Germany! The crabs churn up the bottom of water bodies in such a way that they cause considerable damage to dikes, for example. They increase erosion in river banks and sometimes occur in such masses that they clog water filters on rivers. They are also a problem for commercial fishing and pond management, not only because they destroy fishing nets. They also consume fish caught in fish traps and nets.
But the mitten crab is not considered a problem everywhere in the world; in fact, Eriocheir sinensis is considered one of the most commercially valuable crabs for preparing traditional delicacies in East and Southeast Asia. Their gonads are particularly prized and are among the special delicacies in China, Japan and Singapore. Their market value for industrial use and human consumption ranges from €1 to €3/kg in Asian markets. “Although their consumption has not yet been approved by the European Union, this use could be a way to reduce or control their populations,” suggests Dr. Oliver Hawlitschek, manager at LIB’s molecular laboratory in Hamburg. “This is how other invasive species have been encountered around the world.”
On September 25, Dr. Oliver Hawlitschek will present the mitten crab at the event “Eat this -Change goes through the stomach,” as part of Hamburg Climate Week.
More information:
“Eat this -Change goes through the stomach”, on September 25 in Hamburg, registration: https://tagderstadtnaturhamburg.de/eat-this
INVASIVE SPECIES IN HAMBURG:
The portal www.neobiota-hamburg.de provides information about invasive species in Hamburg. There is not only information about crustaceans, but also about birds, fish, insects and molluscs. And: findings can be reported.
Contact:
Dr. Nancy Mercado Salas
Head of Crustacea Section
Leibniz Institute for the Analysis of Biodiversity Change, Hamburg
Zoological Museum
Phone: +49 40 42 838-2278
E-mail: nancy.mercado.salas@uni-hamburg.de
Dr. Oliver Hawlitschek
Manager Molecular Laboratory
Leibniz Institute for the Analysis of Biodiversity Change, Hamburg
Zoological Museum
Phone: +49 40 42 838-9772
E-mail: Oliver.Hawlitschek@uni-hamburg.de
