The stone crab or thunder crab is a small crab species with big and hard claws. It lives in rock crevices, wood boards along coastal cliffs and mangroves, as well as in calm shells, aquaculture farms… It is very slow, and can cling to rocks very firmly with its bigs claws. The stone crab is prized only for their claws, because the crab body contains very little meat or flesh.
In Vietnam, this crab species is distributed on the coasts of Quảng Ninh and Khánh Hòa provinces, but more popular in Quảng Ninh where it is called cù kỳ. Other local names in Vietnam include: cua đá (stone crab). There are actually two stone crab species in Vietnam: Myomenippe hardwickii and Menippe rumphii. Myomenippe hardwickii is black, while Menippe rumphii is maroon.
The stone crab is also often mistaken with the red egg crab (Atergatis integerrimus, Vietnamese: cù kỳ đỏ) or the red-streaked box crab/ shame-faced box crab (Calappa lophos, Vietnamese: núm, cúm núm) which is also found in Vietnam.
The stone crab can be cooked in crab noodle soup, steamed/roasted crabs, pan-roasted with tamarind, stir-tossed with glass noodle, or can be made into crab meat floss for children.
This stone crab noodle soup utilizes both the claw meat and the crab body. The crab body are ground to make the broth, along with the tomalley in the crab shell. The noodle used in this noodle soup is bún, Vietnamese soft rice vermicelli. Bún noodle can also be replaced with bánh đa, a Vietnamese broad flat noodle (not to be confused with thick round noodle).
In Quảng Ninh, stone crab noodle soup is often sold together with mantis noodle soup. Often, they mix stone crab, mantis shrimp, and tiger shrimp in a noodle bowl.
Mantis shrimps help making the broth sweeter.