"The sales record is really bad because the price is higher than clients' expectation," Sun said.

Besides the higher price, Sun said, Chinese like to buy live fish for cooking, and the frozen ones are not well accepted in the market.

Hairy situation

Even as Chinese consumers tuck into Asian carp to help save US rivers, another invasive species, Chinese mitten crabs, are invading German waters.

But it seems unlikely that Chinese diners will be able to similarly help German waters by eating the crustaceans, also known as Shanghai hairy crabs.

A latest online search failed to show any information involving the sale of the crabs from Germany, even though many Chinese netizens and foodies expressed much interest in them.

Sun Qian, a crab lover in Dalian, Liaoning province, said mitten crabs are delicious and it is a pity that Germans do not seem to care for them.

A netizen going by the online moniker Yilin also posted a "solution" to the problem on a Sina Weibo micro blog that included 20 dishes made of mitten crabs to help entice more palates.

The mitten crab is native to East Asia. In Europe, it was first found in Germany in the early 1900s and has since spread through a number of waterways in northern and central Europe, threatening its water ecosystems by competing with local species and clogging drainage networks.

China's General Administration of Quality Supervision, Inspection and Quarantine has not approved any move to import or sell German mitten crabs in China.

A plan last year to import German mitten crabs for Chinese consumers failed because the Chinese authorities did not give the green light.

In early September last year, Juhuasuan.com, a group purchase website under e-commerce giant Alibaba, took in pre-sale orders for the crabs but had to apologize to customers for failing to deliver. It said customers could claim a full refund and an additional 30 percent compensation for the no-show.

Zhang Jianfeng, the CEO of the website, said the company had not given enough consideration over the procedures to import the crabs on a "large scale".

By Wang Qian

As US law does not allow live fish to be transported across state borders, only frozen fish or fish products can be exported.

The sales manager in Shanghai agreed and said it will take time for Chinese consumers to accept dishes made of frozen fish.

He admitted that the sale of the fish products is not satisfactory yet but he remained optimistic about the business.

For Jia, his company has a special way to "guarantee the best taste for frozen fish".

"After the fish is netted, it will be frozen alive immediately under-28 C. Within 24 hours, the fish will be cut into pieces, put in low-temperature containers and transported by ship," Jia said. The fish will arrive in Tianjin within three weeks, he said.

Besides selling frozen fish, Jia said a processing plant will also be built to produce fish balls, patties and canned food to meet the diversified demand.

"The fish meat tastes better than the fish in China because the water is cleaner in the US and the fish is 100 percent wild and organic," Jia said.

Sourcing solutions

Eating Asian carp is only one way to prevent its spread in US rivers. The US government has spent hundreds of millions of dollars to fight the scourge, including the use of electric barriers, water guns and scent-based lures.

Garvey said the US government has spent nearly $100 million on research in the past four decades to determine ways to impede movement and reduce carp density in rivers.

He expressed worries that the Asian carp will eat freshwater mussels into extinction. The US has the highest diversity of freshwater mussels in the world.

In January, a plan to physically separate the waterway link between the Illinois River and the Great Lakes was unveiled. The move is expected to cost $18 billion and take decades to implement.

There is no guarantee that the permanent separation will become the key way to prevent any interchange between the water systems, Garvey said.

Scientists in the US and China are also strengthening cooperation to study the fish, including the impact of water temperature and flow on its breeding, to seek effective ways to control fish reproduction, Yang said.

In October or November, Chinese scientists will visit the US to further study the fish with US scientists, she said.

Garvey said the US has much to learn from the expertise of Chinese scientists, resource managers, businesspeople and fishermen, and he hopes that the exchange of knowledge on both sides will lead to discoveries that help the US control Asian carp and for China to help recover the species in the Yangtze River.

Yang agreed that the cooperation can help China protect the Yangtze River and recover the fish species.

Amid the increasing construction of hydropower dams of the past decades, overfishing and industrial and agricultural pollution, a report on the Yangtze River jointly conducted by the Ministry of Agriculture and World Wide Fund for Nature last year showed that the ecosystem of the upper river is on the verge of collapse.

Zhao Yimin, head of the Yangtze River Fishery Resources Committee under the Ministry of Agriculture, said in a previous interview that China's fishery resources will be drained soon if no immediate and effective action is taken.

For Jia, compared with the use of "expensive research and technology" to save the rivers in the US and China, delivering Asian carp to Chinese dinner tables is the "fast and cheap" way.