The Chinese Mitten Crab

Abstract

THE Chinese mitten (or woolly-hand) crab, Eriocheir sinensis (see NATURE, June 9, p. 855), was transported to Germany from China in some unknown way and was first caught in the Aller (a tributary of the Weser) in 1912, but was not identified until 1923. It has spread widely in the river systems of Germany—the Elbe, Weser, Rhine and Oder. It is stated that about 700,000 of these crabs were caught in 1931 at Hamburg; the crab has in fact become a pest in some places. The adult crabs wander down the rivers at the beginning of the breeding season; pairing takes place in brackish water of the lower Elbe and Weser, but the crabs bearing eggs are found off the river estuaries in more saline water. In the interests of controlling the crab, Dr. W. Wolterstorff, of the Magdeburg Museum, has addressed questions to the Peking Society of Natural History. These and the answers are contained in the Bulletin of the Society, vol. 8, Part 3, March 1934. Dr. Wolterstorff refers to a report that the crabs were cleared out of the lower Liang Ho River about twenty years ago with nets, as they destroyed the fish, and asks if this was successful. He directs attention to the statement of Prof. Lu-fong of Tientsin that the Chinese consider the crabs holy and hence the crabs caught are not eaten but burnt, and points out that this is at variance with the statement of Marquard that the crab is a popular item of food in China. In reply to the questions, Y. T. Mao, of the Department of Biology, Yenching University, states that Eriocheir sinensis is one of the edible crabs commonly found along the coastal provinces of China and that the Chinese do not consider the crab holy. He adds that according to his observation it is not necessary for the crab to lay its eggs in salt water and that he has not heard that the crabs had to be cleared out from a river at Tientsin, nor has he heard of any river in China inhabited by such a large number of crabs as were stated to occur in the Elbe.