Montana Field Guide

An inhabitant of large, cool rivers, the White Sturgeon is only found in about 170 river miles of the Kootenai River downstream of Kootenai Falls in Montana to Kootenay Lake in British Columbia, Canada (USFWS 1999, Holton et al. 2003). The species is the largest freshwater fish in North America, but this landlocked population is notably smaller than elsewhere in its range. White Sturgeon in Montana have been reported up to 6 ft in length and over 80 pounds (Stephens at el. 2019), while an individual in Kootenay Lake exceeded 350 pounds and was 10 feet in length (Hempsall 2015). Like other sturgeons, these ‘living fossils’ have changed little since the Late Cretaceous (66-100 million years) and may live up to 100 years (Bemis 1997, Krieger and Fuerst 2002, USFWS 1999).

For a comprehensive review of the ecology, conservation status, threats, and management of this and other Montana fish species of concern, please see Montana Chapter of the American Fisheries Society Species of Concern Status Reviews.

Sturgeons have cartilaginous skeletons with a persistent notochord, a protractile tube-like mouth, and sensory barbels on the underside of the snout. White Sturgeon are large fishes with 11 to 14 dorsal, 36 to 48 lateral, and 9 to 12 ventral scutes (bony plates). They are smaller than ocean-going populations, with no reports larger than 200 pounds from the Kootenai River, and are gray in color.

The White Sturgeon population in Montana is part of a landlocked population occurring only in Kootenai River from Kootenai Falls in Montana downstream to Bonnington Falls in British Columbia (USFWS 1993).

Large cold rivers.

The White Sturgeon is a bottom feeder and will eat almost any available organism. They feed mostly on fish, but also eat crustaceans, mollusks, worms, and considerable plant material (Brown 1971, Weisel 1957).

Historically, White Sturgeon responded to spring runoff and warming water temperatures by moving upstream to the spawning areas and preparing physiologically for spawning. Decline in Montana seems to be linked to changes in the Kootenai's flow pattern resulting from completion of Libby dam (Holton 1980, USFWS 1993).

There has been almost no reproduction since 1974 (USFWS 1993). The range in Montana may be part of the breeding area for the population, believed to extend from Shorty's Island, Idaho upstream to Kootenai Falls, Montana (USFWS 1993).

The size and age of first sexual maturity is variable within the species. In the Kootenai watershed, females have been observed to mature as early as age 22 years and males at age 16 years (Paragamian et al. 1997). Females are reported to spawn only once every two to eleven years (Conte et al. 1988, Hanson et al. 1992). Empirical evidence suggests that female White Sturgeon from the Kootenai River exhibited spawning periodicities of over 5 years (Paragamian et al. 1997, Montana AFS Species Status Account).

Throughout their range, White Sturgeon generally broadcast their eggs over clean cobble at depths greater than 6 meters (20 feet) at column velocities less than 0.24 meters per second (0.77 feet per second). Water temperatures associated with White Sturgeon spawning typically ranged from 14 to 20 degrees C. (57 to 68 F.). Empirical embryonic developmental stage and water temperature data were used (Wang et al. 1985) to back-calculate the timing of White Sturgeon spawning events in the Kootenai River, which coincided with lower water temperatures (8.6 to 12.9 C.). Spawning has occurred at relatively low discharges (13 to 20 kcfs) and over finer substrate than is considered optimal for egg to fry survival. It remains uncertain whether any juveniles survive when eggs are dispersed over fine substrates. Furthermore, several potentially important early life (post-fertilization) mortality factors, and possible intermittent female stock limitations, have been suggested as mechanisms to explain prolonged (more than 25 years) White Sturgeon recruitment failure in the Kootenai River (Anders and Richards 1996, Anders et al. 2002, Montana AFS Species Status Account).

The Kootenai River population of White Sturgeon (Acipenser transmontanus) was listed as endangered under the Endangered Species Act (USFWS 1994), due to a lack of juvenile recruitment to the population since the mid-1960s. Almost no recruitment has occurred since Libby Dam began regulating the Kootenai River in 1972 (Duke et al. 1999, USFWS 1999). In the final rule, the Service stated "there is no recent evidence of successful spawning and survival past the egg stage" and "regulations and experimental flow programs have not been effective in arresting the decline of the species". A small number of recruits from a cohort spawned in 1974 indicated fairly successful natural reproduction, associated with high, protracted springtime river flows. Between 1992 and 2000, the wild population was augmented with 4,879 juvenile White Sturgeon (age 1 and 2) from the Kootenai Tribal Conservation Aquaculture Facility located in Bonners Ferry, Idaho, to address concerns of increasing demographic and genetic risk to a non-recruiting population (Ireland et al. 2002, Montana AFS Species Status Account).

Recovery of the White Sturgeon population in the Kootenai River is contingent upon re-establishing natural recruitment, minimizing additional loss of genetic variability, and successfully mitigating biological and habitat alterations that continue to harm the population. The White Sturgeon Recovery Plan (USFWS 1999) recommends simultaneous implementation of three high priority recovery approaches: 1) augment spring flows in the Kootenai River to enhance natural production; 2) implement a conservation aquaculture program to prevent extinction and preserve genetic variability; and 3) re-establish suitable habitat conditions to increase White Sturgeon survival past
the embryonic and larval stages (Montana AFS Species Status Account).

The Kootenai River White Sturgeon Study and Conservation Aquaculture Project was initiated to preserve the genetic variability of the population, begin rebuilding natural age class structure, and prevent extinction while measures are implemented to restore natural recruitment (Anders and Westerhof 1996, USFWS 1999, Ireland 2000, Ireland et al. 2002). A breeding plan has been implemented to guide management in the systematic collection and spawning of wild adults before they are lost from the breeding population (Kincaid 1993). The implementation of the breeding plan includes measures to minimize potential detrimental effects of conventional stocking programs (Montana AFS Species Status Account).

Additional information on the biology and management of White Sturgeon populations can be found on the U.S. Fish and Wildlife Service's Environmental Conservation Online System Species Profile