The living fossil that still patrols the rivers of the Pacific Coast recently received a boost from the US government, which listed the green sturgeon as "threatened" under the Endangered Species Act, effective April 6th. While the ruling is needed to improve the health and outlook for the species, the new listing--authorized by a final ruling by the National Marine Fisheries Service--only applies to the southern population, and may fail to protect these fish leaving California's Sacramento River System unless stiff measures are applied over a wide geographical range, said the Wildlife Conservation Society (WCS).
"We support the 'threatened' listing of green sturgeon under the ESA; it is based on good science and we feel that this is a step in the right direction," said WCS researcher Dan Erickson, one of the leading experts on the species. "However, managers will have to craft regulations carefully to protect this southern population of green sturgeon, which are highly migratory and thus vulnerable to threats in Oregon and Washington coastal waters, and even impacts in Canada."
Eventhough the northern population of green sturgeon, which spawns in the Klamath River in California and the Rogue River in Oregon, is genetically distinct from this southern population that is now listed as Threatened, individual fish from each separate population most likely frequent the same coastal waters. As per archival-tagging studies conducted by Erickson, green sturgeon travel great distances from their ancestral rivers; individual fish from Oregon's Rogue River were tracked as far north as northern Vancouver Island, Canada, providing support to the theory that both populations likely interact with one another. Understanding the behavior and migratory patterns of these two populations are therefore important considerations for improving current regulatory frameworks for the species.
"We're hoping that additional findings on how the two populations move and interact can further inform the listing of these fish populations in order to bring the management of the green sturgeon into regulatory consistency," added Erickson.
Eventhough demand for the species has never been high, commercial and recreational fisheries are just one of the threats now faced by green sturgeon. Factors such as loss of suitable habitat, decreased water quality, and an increase in predators, impact the long-term survival of the species. Fish and Wildlife Commissions in both Oregon and Washington have set a 5-foot maximum size limit to limit the sport and commercial catches to mostly immature juveniles and to protect breeding adults, which can grow larger than 7 feet in length and live more than 60 years. California recently banned the retention of green sturgeon by all fisheries.
Worldwide, a number of populations of the 25 species of sturgeon have been brought to the brink of extinction by many human-related factors, especially the beluga sturgeon of the Caspian and Black Seas, which is the source of the world's finest and most sought-after roe, known as caviar. Imports of beluga caviar are now banned by the United States Fish and Wildlife Service.
Posted by: Kelly Source