Hairy crabs

It's hairy crab season and street vendors and Shanghainese restaurants have refrigerated cases displaying the deep-green crustaceans.

What are they? A species of crab distinctive for the fine hairs on their claws. Although they have a small amount of sweet meat, these crabs are eaten primarily for the female roe and the male sexual organs and sperm (most people euphemistically refer to these male parts as roe). The ones we get

in Hong Kong come from the mainland but they can theoretically thrive in any freshwater lake in which the conditions are right. The best hairy crabs are said to come from Yang Cheng Lake, in Jiangsu province, near Shanghai, but its yield forms only a small percentage of all the hairy crabs on the market.

What are the differences? Male roe is softer and smoother than its female counterpart. To tell the difference between male and female crabs, look at the flap on the underbelly; it's rounded and bell-shaped in females and pointed in males.

How to choose? The crabs are priced by weight, not size. Weigh the crabs and pick the ones that seem heavy for their size - they contain more roe. They should be alive.

What else? Yang Cheng crabs, which have white bellies and lighter hairs on their claws, are said to have sweeter, more fragrant meat and roe. There is such demand for them they command top dollar and a counterfeit industry has been built around them, so buy your crabs from a reputable vendor.