Lobster vs Crayfish

In a loose but fair sense, yes. Crayfish and the clawed lobsters are close relatives within the decapod crustaceans, built on the same body plan and behaving in much the same way, and a crayfish looks like a miniature lobster because in evolutionary terms it more or less is one. The two lineages diverged as one group stayed in the sea and grew large and long-lived, while the other colonised fresh water and stayed small. Crayfish are sometimes marketed as freshwater lobster or, in France, as ecrevisse, and the Tasmanian giant freshwater crayfish blurs the line further by reaching genuine lobster size.

They are all the same kind of animal under different regional names. Crayfish is the standard term in Britain, much of the United States, and scientific use. Crawfish is common in the southern United States, especially Louisiana, where the crawfish boil is a culinary institution. Crawdad and mudbug are informal American names. Yabby, marron, and koonac are Australian names for particular native species. Ecrevisse is the French name. All refer to freshwater decapod crustaceans of the crayfish families. To confuse matters, in some parts of the world spiny lobsters are also called crayfish or crawfish, but those are marine animals without claws.

Yes, and the flavour is similar, sweet and mild, though a crayfish yields far less meat, concentrated in the tail with a little in the claws of the larger species. Because they are small, crayfish are usually cooked and served in bulk, boiled in heavily spiced water and eaten by hand, as in a Louisiana crawfish boil or a Scandinavian kraftskiva, rather than presented as a single centrepiece like a lobster. Crayfish are also farmed widely, particularly in China, Louisiana, and Scandinavia. One caution is that several invasive crayfish, such as the American signal crayfish in Europe, are both edible and ecologically damaging, so eating the catch is sometimes encouraged as a control measure.