decapod crawfish or crayfish WIKIPEDIA:Crayfish Crayfish, often referred to as crawfish or crawdad, are freshwater crustaceans resembling small lobsters, to which they are closely related. They are found in bodies of fresh water that do not freeze to the bottom, and which have shelter against predators. Most crayfish cannot tolerate polluted water, although some species such as the invasive *Procambarus clarkii* are more hardy. Some crayfish have been found living as much as 3 m (10 feet) underground. There are three families of crayfish, two in the Northern Hemisphere and one in the Southern Hemisphere. The Southern Hemisphere family *Parastacidae* lives in South America, Madagascar and Australasia, and is distinguished by the lack of the first pair of pleopods. Of the other two families, members of the *Astacidae* live in western Eurasia and western North America and members of the family *Cambaridae* live in eastern Asia and eastern North America. [https://en.wikipedia.org/wiki/Crayfish] astacidae astacoidea cambaridaa cambarus spp. crawfish crayfish parastacidae procambarus spp. requires discussion