The Chinese mitten crab - hairy crab, dazhaxie - is a small freshwater crab with a fringe of dark hair on its claws, native to the rivers and lakes of the lower Yangtze. It lives in fresh water and migrates to the sea to breed, and the autumn migration is when it is caught: the season runs roughly from late September into December, with the female crabs prized for their roe and the males for their paste. In Shanghai the season is a fixed point of the calendar, and restaurants advertise it the way other cities advertise game.
Why it matters
The crab is small - a good one weighs a few hundred grams - and most of that is shell. What people are paying for is the orange roe inside the female and the rich, dense paste in the male, both of which are eaten with vinegar and ginger. The meat in the claws and legs is sweet and delicate but laborious to extract. A proper meal involves a pick, a small spoon and a great deal of time; there is no efficient way to do it, and the process is the pleasure.
How it is served
The classic preparation is steaming, with nothing added, served cold or hot with a dipping sauce of black vinegar and shredded ginger, and warm yellow rice wine alongside. Beyond that, the crab appears as roe stirred through tofu, as crab roe noodles, in soup dumplings, and in a laborious dish in which the meat and roe are picked out by hand and served in the shell - which is why that dish costs what it does. Crab roe noodles and crab roe xiaolongbao are the accessible versions if you do not want to work for your dinner.
Practical notes
Prices move a lot through the season: the first crabs in late September are the most expensive, and quality peaks from October into November. Cheapest and best value is a crab bought at a wet market and steamed at home or at a small restaurant that charges a cooking fee. Don't eat the lungs or the gills, and don't drink iced drinks with crab. The season also runs in the lakes around Suzhou and Taihu, and day trips to the lake towns to eat crab are a Shanghai autumn tradition in themselves.
