Chinese mitten crab facts for kids
Quick facts for kids Chinese mitten crab |
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| Scientific classification |
| "Chinese mitten crab" | |||||||||||
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| Traditional Chinese | 大閘蟹 | ||||||||||
| Simplified Chinese | 大闸蟹 | ||||||||||
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| Alternative Chinese name | |||||||||||
| Chinese | 上海毛蟹 | ||||||||||
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The Chinese mitten crab, also known as the Shanghai hairy crab, is a medium-sized burrowing crab that is named for its furry claws, which resemble mittens.
Its import and trade is forbidden in the whole of the European Union.
Contents
Description
This species' distinguishing features are the dense patches of dark setae on its claws. The crab's body is the size of a human palm. The legs are about twice as long as the 3–10-centimeter-wide (1–4 in) carapace.
Chinese mitten crabs spend most of their life in fresh water and return to the sea to breed. The crabs have a lifespan around one to five years.
Distribution and habitat
The species is native to rivers, estuaries and other coastal habitats of East Asia from Korea in the north to Fujian, China in the south. It has also been introduced to Europe and North America, where it is considered an invasive species.
The types of estuaries suitable for the mitten crab include large brackish waters for the larva to develop in, and large shallow waters for the growth of the juvenile crabs.
The Chinese mitten crab originates from Hong Kong to the border of Korea. It can be found inland but prefers coastal areas. In the Yangtze, the largest river in its native range, Chinese mitten crabs have been recorded up to 1,400 km (760 nmi) upstream. It is known to settle in rice fields by the sea and rivers inland. The crab is found in subtropical and temperate regions.
Diet
The mitten crab diet is omnivorous. Their main prey consists of worms, mussels, snails, dead organic material, and other small crustaceans and fish.
An increase in microplastics has had a significant impact on the population as it affects their metabolism, growth, and oxidative stress response in the liver.
Reproduction
Mitten crabs migrate from freshwater to saltwater for breeding. In late August, they begin migrating downstream to the sea, away from their feeding grounds. The crabs begin to breed in the brackish waters in late fall. The males arrive first and stay in the brackish waters all winter; the females arrive after. The eggs are laid within 24 hours of mating, then attached to the abdomen of the female. After the eggs are attached, the female leaves immediately, heading to the mouth of the river. The larvae hatch from the eggs during the summer, after which they float and drift about the brackish waters. Because the journey to breed for crabs is so great, they only breed once during their lifetimes. The breeding age is normally toward the end of their lifespans. The crabs have sizable egg production count since these crabs only breed once. After the crabs successfully reproduce, they have very little energy and begin to waste away.
Different life stages of the mitten crab:
- Eggs require pure salt water to mature.
- Larvae hatch from the eggs in brackish waters.
- The larvae gradually move from brackish water to fresh water.
- The final stage of the larvae is the megalopa, which is 3–4 millimeters (1⁄8–5⁄32 in) in length.
- The megalopa then develop into small mitten crabs in the freshwater.
Invasiveness
This certain species of crab has been spreading rapidly from Asia (China and Korea) to North America and Europe, raising concerns that it competes with local species, and its burrowing nature damages embankments and clogs drainage systems. The crabs can make significant inland migrations.
It is generally illegal to import, transport, or possess live Chinese mitten crabs in the United States.
Chinese mitten crabs have also invaded German waters, where they destroy fishing nets, hurt native fish species and damage local dams, causing damage of up to 80 million Euros.
The first time the crab was brought to Europe was most likely by commercial vessels. Ships must fill their ballast water tanks and during one of these filling events, it could have been the spawning time for the mitten crab. Since the larvae are free floating and 1.7–5 millimeters (1⁄16–3⁄16 in) in size, it would have been easy for them to be swept into the ballast water tank. Once the ship reached Europe and emptied its tank, the crab larvae were released. Over time, this repetition would allow for a prominent mitten crab population in Europe. The crab has spread and can be found in Continental Europe, Southern France, United States of America (the San Francisco Bay), and the United Kingdom.
Culinary
Crabs are a delicacy in Shanghai cuisine and eastern China.
Crabs from Yangcheng Lake are especially prized, since they are perceived to have sweeter meat. Most of the Yangcheng crabs are exported to Shanghai and Hong Kong, and high-profit foreign markets.
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Hairy crab is an important part of Shanghai cuisine
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Closeup of the roe inside a steamed female crab
Management efforts
Management efforts have been shown to be very difficult. This is due to its abundance, high reproductive rate, and high physiological tolerance. All the following efforts were attempted but showed little improvement: "catch as many as you can", migration barriers, trapping, raising awareness, electrical screens, and pulses.
There has been a discussion of capturing the breeding crabs at the river mouths. There have been difficulties in carrying out this plan though. Other strategies such as capturing them when they pile up at dams have proven somewhat effective. The problem arises when the crabs climb the walls of the dams and over into the rivers behind the dams.
See also
In Spanish: Cangrejo chino para niños
