Critical habitat (CH) is designated for the survival and recovery of species listed as threatened or endangered under the Endangered Species Act (ESA). Critical habitat includes those areas occupied by the species, on which are found physical and biological features that are essential to the conservation of an ESA listed species and which may require special management considerations or protection. Critical habitat may also include unoccupied habitat if the Secretary determines that the unoccupied habitat is essential for the conservation of the species. Critical habitat is designated by regulation at the time a species is listed under the ESA unless it is not prudent to do so or it is not determinable at the time. If it is not determinable, then NMFS must designate CH no later than one year after publication of a final listing. After identifying areas that meet the definition of CH, NMFS conducts an analysis to determine whether the economic, national security, or other relevant impacts of designating some areas as CH outweigh the benefits to the species. If so, NMFS may exclude such areas from the final CH designation. Each proposed and final regulation is published in the Federal Register. The final CH designation is also published in the Code of Federal Regulations (50 CFR 226).