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NATURAL HISTORY

KOOTENAI RIVER WHITE STURGEON } Acipenser transmontanus
FAMILY: Acipenseridae

DESCRIPTION: Sturgeon have cartilaginous skeletons and a tube-like mouth. In the Kootenai River, they can grow to be larger than 200 pounds. They are gray in color.

HABITAT: Kootenai River white sturgeon live in the freshwater of the Kootenai River. Their ideal habitat includes a clean cobble substrate conducive to insect production and sturgeon egg incubation, undiked side channels and low-lying deltaic marsh lands, and waters affected by seasonal floods that promote the exchange of nutrients and organisms. Modification of the Kootenai River has dramatically altered white sturgeon spawning, egg incubation, and rearing habitats.

RANGE: The Kootenai River population of white sturgeon is one of 18 landlocked populations of white sturgeon found in the Pacific Northwest. This population is restricted to approximately 168 miles of the Kootenai River in Idaho and Montana and Kootenay Lake in British Columbia, Canada.

MIGRATION: Kootenai River white sturgeon have historically migrated freely in the Kootenai River, but their upstream migration to spawn has been virtually halted by the effects of Libby Dam.

BREEDING: These fish have specific requirements for water temperature and substrate when laying eggs, and any alteration may make reproduction impossible. There has been almost no reproduction in the Kootenai River white sturgeon population since 1974.

LIFE CYCLE: Sturgeon can live to be up to 100 years old, but in the Kootenai watershed they are not as long-lived. Females have been observed to mature as early as age 22, with males sometimes maturing at 16. Females are reported to spawn once every two to 11 years.

FEEDING: White sturgeon are bottomfeeders. They will eat almost any available organism; though they feed mostly on fish, they also eat crustaceans, mollusks, worms, and plant material.

THREATS: The operation of Libby Dam has altered the sturgeon’s Kootenai River habitat by reducing spring peak flows by more than 50 percent and increasing winter flows by nearly 300 percent, removing almost all possibility of sturgeon reproduction.

POPULATION TREND: In decline since the mid-1960s, the Kootenai River white sturgeon population has had almost no reproduction since 1974.

 

Photo by Pete Rust, Idaho Fish and Game