White Sturgeon

White Sturgeon

White Sturgeon

Sturgeon have remained nearly unchanged for at least 70 million years. Sturgeon fossils over 200 million years old show that sturgeon lived when dinosaurs roamed Earth. Historically, white sturgeon ran along the Pacific Coast from the Aleutian Islands to central California, spawning mostly in the Fraser, the Columbia, and the Sacramento-San Joaquin river systems. The largest specimen on record, taken near the mouth of the Fraser River in 1897, weighed 1,387 pounds.

Of 18 landlocked white sturgeon populations, the Kootenai River contains the only population that was naturally isolated from the lower Columbia River drainage. All the other populations were isolated by hydroelectric and irrigation facilities. It is believed the Kootenai population became isolated upstream of Bonnington Falls, located below Kootenay Lake British Columbia, during the last period of glaciation at least 10,000 years ago. Kootenai white sturgeon are now restricted to 168 river miles between Kootenai Falls, 31 miles below Libby Dam, and Kootenay Lake in British Columbia. This separation made the Kootenai River population genetically unique.

The Kootenai River white sturgeon was listed as endangered in 1994. This population had been declining for at least forty years and natural reproduction has been insignificant since 1974. Kootenai sturgeon began declining in the 1950s and 1960s as water quality deteriorated due to pollution and as loss of river sloughs and marshes left fewer rearing areas for juvenile fish. Libby Dam, completed in 1972, drastically changed the Kootenai River ecosystem by disupting the natural flow regime and altering seasonal and daily water temperatures. Nutrient retention behind the dam and unnatural river fluctuations negatively impact biological production in the river, as evidenced by reduced numbers and growth rates of resident trout, and whitefish.

According to state, federal, and Kootenai Tribe of Idaho biologists, the Kootenai River sturgeon population declined from an estimated 1,194 fish in 1982 to less than 600 individuals by 2004. Based on a 9 percent annual attrition rate, researchers predict that all remaining wild adults will vanish by 2065. The population will be functionally extinct by 2035.

Fishing for white sturgeon has been illegal in Montana since 1979. Idaho ended the sport harvest of white sturgeon in the Kootenai in 1984, and white sturgeon fishing in the British Columbia portion of the Kootenai system was halted in 1990. Lack of reproduction is the most immediate threat to the Kootenai sturgeon population. Despite experimental discharges from Libby Dam designed to benefit spawning and egg development, recruitment has not improved. Fortunately, before the last wild adults vanish, 3,000-6,000 of their progeny from the Kootenai Tribe of Idaho's sturgeon aquaculture facility will have survived to maturity (at 30 years old). Since 1990, the Kootenai Tribe of Idaho has propagated white sturgeon in captivity and thousands of juvenile sturgeon have been released into the Kootenai River in Idaho.

Montana has less than 30 miles of white sturgeon habitat in the Kootenai River. In 1980, only a handful of adults attempted to spawn in this section of river. Researchers captured a single adult several times in Montana between 1990 and 1992. Twenty juveniles have been planted in Montana's portion of the Kootenai River. The first 10 fish, planted in the late 1990s, returned to Idaho. Ten juveniles equipped with radio tags were planted in 2004 and nine remain in Montana as of August 2004. The recovery team hopes to plant larger numbers of juveniles in Montana during 2005. Researchers hope these fish will return to suitable spawning habitat in Montana when they mature in 30 years.

Recovery of the white sturgeon requires natural reproduction. Evidence suggests that a naturalized spring freshet is needed to initiate migration to the spawning reach. Spawning now occurs in Idaho over sand substrate unsuitable for survival. The historic spawning reach, which is thought to be further upstream, is heavily embedded with sand. Before Libby Dam was installed, the natural spring freshet flushed fine sediments from spawning cobble. The US Fish and Wildlife Service's 2000 Biological Opinion implemented a tiered flow strategy to assess possible thresholds between recruitment success and failure. The Service also recommends increasing the discharge capacity of Libby Dam by 5,000 cfs in 2004 and an additional 5,000 cfs by 2007. Unfortunately, Libby Dam cannot currently pass the additional 10 kcfs without the use of the spillway, and a spill of less than 2 kcfs exceeds Montana's water quality standard of 110 percent gas supersaturation. Excess gas causes gas bubble trauma in river fish including federally listed (threatened) bull trout. Therefore, researchers are analyzing alternative ways to flush sediments and provide suitable rearing habitat without releasing high river flows that may be prevented by human development in the flood plain.

Survival of the species and public acceptance of recovery actions require shifting emphasis from a high spring peak to a gradually descending hydrograph, and from the spawning period to survival during the crucial first few months of life. Learn more