In 2001, the National Marine Fisheries Service (NMFS) received a petition requesting Endangered Species Act (ESA) listing of North American green sturgeon (Acipenser medirostris) as a threatened or endangered species. In response to this petition, NMFS announced that it would initiate an ESA status review. The ESA allows the listing of A Distinct Population Segments@ (DPSs) of vertebrates as well as named species and subspecies. The combined U. S. Fish and Wildlife Service and NMFS policy on recognition of DPSs outlines two tests to identify separate units: discreteness and significance. A DPS may be considered discrete if it is markedly separate from other populations of the same taxon as a consequence of physical, physiological, ecological, or behavioral factors or if it is delimited by international governmental boundaries. The significance of the population will be decided on the basis of considerations including, but not limited to its persistence, evidence that loss of the DPS would result in a significant gap in spatial structure, evidence of the DPS representing the only surviving natural occurrence of a taxon, or evidence that the DPS differs markedly in its genetic characteristics. Once a DPS has been identified, a risk assessment is preformed to determine whether a listing is warranted for that unit.
Green sturgeon have a complex anadromous life history. They spend more time in the ocean than any other sturgeon. The majority of green sturgeon are thought to spawn in the Klamath River, but spawning also occurs in the Sacramento and Rogue rivers. First spawning occurs at 15 years for males and 17 years for females. Female green sturgeon are thought to spawn only every 5 years. Adults migrate into rivers to spawn from April to July with a May to June peak. Eggs are spawned among rocky bottom substrates and juveniles spend 1 to 4 years in freshwater.Keyword Tags: