According to Montana Fish, Wildlife & Parks, the average lifespan of crayfish is between two and three years. These crustaceans tend to grow to 3 or 4 inches long in Montana but have been known to grow up to 16 inches long in southern states.
The crayfish, which is the most common crustacean in the world, is also known as a crawfish or crawdad. There are nearly 400 species of crayfish in North America. The term "cray" is believed to have been derived from the word "crevice," most likely because crayfish love to crawl into rocky crevices along river bottoms. Crayfish are freshwater crustaceans found in rivers, streams, ponds, lakes and marshes.