The same root

Both Panjin crabs and their Yangchenghu relatives have the same name - Eriocheir sinensis, or Chinese mitten crab. They live in different environments. Panjin crabs are found in reed ponds or paddy fields. Those in Yangchenghu mature in lakes. Due to the different temperature, the former's growing period is shorter than the latter. As a result, Panjin crabs are usually smaller than their Yangchenghu relatives, according to Wang.

Both crabs may share the same megalopa, or final larval stage. According to the Ocean and Fisheries Bureau of Panjin, during the period of the 11th Five-Year Plan (2005-10), the city offered more than 40,000 tons of larval crabs to at least 20 cities and provinces, which accounted for 70 percent of the country's total supply.

"There are no significant differences between the two except their sizes due to different climates, water quality and other factors," Wang added.

"If you have to find something different between the two, Panjin crabs are usually heavier than the Yangchenghu crab if they are the same thickness, length and width," said Yan from the Panshan county crab industry association.