Wildlife experts in the area, called the Zhejiang province, are less than thrilled.
Turns out this season is a critical period for the hairy crabs, also known as Eriocheir sinensis or the Chinese mitten crab, who migrate downstream in the fall to reproduce and then lay their eggs.
A threat to crab migration
Most fish, including salmon, striped bass, and sturgeon, have the opposite breeding pattern of hairy crabs. They're anadromous, meaning they hatch in fresh water, migrate to salty, brackish waters at sea (where they spend the majority of their lives), and return to fresh water to breed. By contrast, hairy crabs are catadromous, meaning they hatch in brackish sea water, spend the majority of their lives in freshwater, and return to brackish salt water to breed.
Dumping thousands of them into China's Qiantang River, where the man reportedly wanted to release them, could disrupt their population's migratory patterns, according to the South China Morning Post.
The Post reports that Chinese authorities are also worried about the origin of the purchased crabs. After hairy crabs were introduced to Germany in the 1930s, where they are recognized as an invasive species, Germany began exporting them back to China.
Depending on where they came from initially, they could bring with them foreign bacteria and potentially disrupt the delicate balance of aquatic life in the Qiantang.
Invasive species
Worldwide, hairy crabs are considered one of the top 100 worst invasive species.
In the US, they are classified as "injurious wildlife," which prohibits them from being imported or transported between any states without a federal permit. In Europe, where they were likely introduced by traders during the Opium Wars of the 1930s, hairy crab populations are thriving, to the dismay of authorities there.
The crabs were accused of causing millions' worth of damage to German dams in 2012, so the country began exporting them back to China. According to the BBC, the crustacean "preys and on native species and causes severe structural damage to riverbanks."