The North American green sturgeon is a large anadromous fish that ranges from Alaska to Mexico in marine waters, feeds in estuaries and bays from San Francisco Bay to British Columbia, and spawns in fresh water in the mainstem of only a handful of large rivers. The remaining green sturgeon populations exist in rivers that have been extensively dammed, diverted, and polluted. Sturgeons in general are highly vulnerable to habitat alteration and over-fishing because of their specialized habitat requirements, the long time it takes them to reach breeding maturity, and their episodic reproductive success. The large size and sluggish nature of sturgeons make them easy to net and snag.
Recent genetic studies show that the Asian forms (including the "Sakhalin sturgeon" of Russia) of the green sturgeon can be considered a separate species (Acipenser mikadoi) from the North American green sturgeon. Regardless of taxonomy, the green sturgeon appears to be in trouble throughout its range. It is apparently extinct in Japan, endangered in Russia, and has been given "rare" status in Canada. The information presented in this petition shows that the North American green sturgeon has a high risk of extinction.
The only remaining spawning populations of North American green sturgeon are in the Sacramento and Klamath River basins in California and possibly in the Rogue River in Oregon. These rivers all have flow regimes affected by water projects, limiting suitable spawning conditions for green sturgeon. Increasing urban and agricultural demand for water from these rivers potentially threatens the future spawning success for the entire species. The southernmost green sturgeon populations occur in California, a region experiencing dramatic declines of its anadromous fishes due to dams, water withdrawals, and habitat alteration. A number of presumed spawning populations of green sturgeon have been lost since the 1960s and 1970s (in the Eel River, South Fork Trinity River, and San Joaquin River). Severe declines of green sturgeon have been noted recently in northern rivers which may have once had spawning populations, such as the Umpqua River in Oregon and the Fraser River in Canada.
The history of sturgeon fisheries throughout the world has been one of overexploitation followed by severe population reduction. Although there is not much historic data on green sturgeon, early accounts from fishermen and the well-documented collapse of the Columbia River white sturgeon fishery due to over-fishing indicate that green sturgeon stocks were likely severely depleted before the turn of the century. Further declines in abundance were noted in the mid-20th century due to continued over-harvest and habitat destruction.
Although more restrictive size limit restrictions have been gradually implemented, present fisheries probably continue to deplete a stock of large, old fish that cannot renew itself at present harvest rates. Until recently, various west coast fisheries were harvesting at least 6,000 to 11,000 green sturgeon per year. In recent years, these fisheries have been harvesting a conservatively estimated minimum of 3,000 to 5,000 green sturgeon annually. Although statistics are incomplete, it is likely that fishing pressure has been increasing as Pacific salmon and white sturgeon stocks decline. Of particular concern are commercial fisheries in the Columbia River and Washington coastal region, and the developing tribal gill net fishery on the Klamath River, which targets the largest known spawning population of green sturgeon.
The principal fisheries for green sturgeon are in south coastal Washington and in the nearby Columbia River estuary, yet there is no evidence of sturgeon spawning in that region. These fisheries may depend on sturgeon from California that are attracted to the area for abundant food resources. Recent Oregon and Washington trawl catch statistics show evidence of continued green sturgeon decline. There has been a dramatic decline of trawl by-catch of green sturgeon off Vancouver Island and in the salmon net fishery in the lower Fraser River in Canada. The trawl catches are good indexes of abundance since green sturgeon are not targeted by these fisheries, but are taken incidentally.
It is currently estimated that each of the three known or suspected spawning populations of green sturgeon probably contain a few hundred mature females, at best (Musick et al. 2000). This is cause for alarm, because with so few females of reproductive age, not only do fish have a hard time finding each other for spawning, but also maintaining minimum population sizes for genetic diversity becomes a concern. Green sturgeon are particularly at risk because their ecology and population structure are so poorly studied and understood.
A 1992 NMFS status review of the species in California (Moyle et al. 1992) made a "conservative" recommendation that the green sturgeon be regarded as a threatened species. The American Fisheries Society (Musick et al. 2000) recently reviewed the risk of extinction for marine fish in North American waters and determined that the green sturgeon is endangered, noting an 88% decline in most of its range. The green sturgeon clearly warrants prompt listing as an endangered or threatened species under the Endangered Species Act.
ENVIRONMENTAL PROTECTION INFORMATION CENTER
CENTER FOR BIOLOGICAL DIVERSITY
WATERKEEPERS NORTHERN CALIFORNIA
PETITIONERS
JUNE 2001
