Alkali Fairy Shrimp (Branchinecta mackini) is a large (18-20 mm) freshwater branchiopod that is found west of the continental divide from British Columbia, Canada to Mexico. In New Mexico they are found in Luna County. They inhabit temporary pools and wetlands that are cloudy and alkaline. Their habitats increase in salinity as the pools dry and eggs only hatch when salinity is low.