Current Range and Status: Today, pallid sturgeon populations are fragmented by mainstem dams on the Missouri River. The pallid sturgeon are scarce in the upper Missouri River above Ft. Peck Reservoir; in the Missouri and lower Yellowstone Rivers between Ft. Peck Dam and Lake Sakakawea; in the Missouri River downstream of Gavins Point Dam; and in the Mississippi and Atchafalaya Rivers.

Habitat: Pallid sturgeons evolved and adapted to living close to the bottom of large rivers with high turbidity and a natural hydrograph. Their preferred habitat has a diversity of depths and velocities formed by braided channels, sand bars, islands, sand flats and gravel bars.

Life History and Reproductive Biology: Sexual maturity for males is estimated to be 7-9 years with up to 3 years between spawns. Females are not expected to reach sexual maturity until 7-15 years, with up to 10-year intervals between spawning. Pallid sturgeons are long lived, with individuals perhaps reaching 60 years of age or more.

Reasons for Decline: All of the 3,350 miles of river habitat within the pallid sturgeon's range have been adversely affected by our attempts to tame the rivers. Approximately 28% has been impounded, which has created unsuitable lake-like habitat and blocked migration routes; 51% has been channelized into deep, uniform channels; the remaining 21% is downstream of dams which have altered the river's hydrograph, temperature and turbidity. Hybridization with the more common shovelnose sturgeon is a threat to the species and may be attributed to the modifications occurring to the habitats used by both species. Commercial fishing and environmental contaminants may also played a role in the pallid sturgeon's decline.

Recent Recovery Activities: Population augmentation and propagation has been a focus of scientists since the mid 1990's when it was realized that recruitment of juvenile fish into the permanent population is not occurring at levels that will sustain the species. The current populations are composed of older fish that will die off in the near future. Since pallid sturgeons do not reach maturity until possibly 12 to 15 years of age, and spawning interval may be several years apart, we must stock now so that we have adults in the wild when habitats are restored. The juvenile pallid sturgeon we stock today will be the breeding population for future recovery efforts. However, habitat restoration will be essential to realize the recovery of this species. Habitat restoration, life history information and threats to the species remain in the forefront of recovery issues.

Pallid Sturgeon: Status as of 05/01
 

 

Pallid sturgeon evolved within the diverse environments of the Missouri and Mississippi Rivers at a time when flood plains, backwaters, chutes, sloughs, islands, sandbars, and main channel waters formed the large-river ecosystem. They were well adapted to living in large rivers where fluctuating environmental conditions, such as river flows, exist. Those same characteristics that enabled the pallid to survive for thousands of years have also made them vulnerable to changes in the river that diminished spawning and nursery habitat.

In the biological opinion on Missouri River operations, the U.S. Fish and Wildlife recommends returning the river to more natural flows. Here is how the Service=s recommendations will benefit pallid sturgeon:

The Service has recommended an increase of warm spring flows from Fort Peck Dam spillway to maximize the amount of warm water habitat available below the dam. Reproduction by warm water species such as the pallid has been limited due the cold water coming from the dam. Warm water intentionally spilled over the spillway will act as a reproductive trigger for native fish - including the pallid sturgeon.

A modest increase of flows from Gavins Point dam in the spring will also provide biological cues to encourage pallid sturgeon to spawn.

Lower summer flows are expected to benefit pallid sturgeon in the lower 800 miles of the river by providing additional slow, shallow water to allow young-of-the-year fish to grow large enough to survive through the first winter. 

Larval and fingerling pallids need to remain in shallow water areas containing high concentrations of nutrients. Under present conditions, the Missouri River is simply too fast and deep throughout much of the lower basin to provide the shallow and slack water habitat where young fish can rest, feed, and grow until they are capable of negotiating main channel currents.

Flow modifications in conjunction with habitat restoration are critical to ensure the continued existence of this Missouri River resident.