As long-term telemetry efforts continue in the Lower Missouri River, observations of repeated patterns of migration, site fidelity, and tributary use are more common. The relative value of tributaries to the recovery of the species is as yet unknown. Telemetered pallid sturgeon have been located in the Osage River as far as Lock and Dam 1 (12 miles upstream from the confluence with the Missouri River) and have remained in the tributary from spring through early fall. Pallid sturgeon have been shown to use other Missouri River tributaries including the Grand, Kansas, Platte, and Big Sioux rivers. Tributaries like the Osage River may provide important habitat for overwintering, aggreation or refuge, feeding opportunities, or reproductive requirements of the species in the highly modified Missouri River basin.
This spring, the U.S. Fish & Wildlife Service – Columbia Fish & Wildlife Conservation Office, in collaboration with the U.S. Fish & Wildlife Service – Columbia Ecological Services Office, is continuing sampling that began last year to determine if pallid sturgeon use the Osage River. They will also continue to determine if Lock and Dam 1 is a barrier to sturgeon upstream movement. In two weeks of sampling (April11-22, 2011), USFWS caught eight pallid sturgeon just downstream of the Lock and Dam 1 structure.
Complementary to the U.S. Fish & Wildlife Service sampling efforts, the USGS Columbia Environmental Research Center conducted an underwater sonar survey below Lock and Dam 1 using dual frequency identification sonar (DIDSON). DIDSON is an advanced type of sonar that uses sound waves to produce underwater imagery of fish and their habitat in deep or turbid water where light cannot penetrate. The high-resolution imagery from the DIDSON is collected at high speed and can be played back to create moving images that can be used to identify fish and observe their behavior. DIDSON imagery revealed multiple strugeon in the vicinity downstream of Lock and Dam 1. DIDSON surveys in the lock itself did not detect any sturgeon, suggesting that it may not provide effective upstream passage. Observations of large numbers of sturgeon aggregating below the dam, and the sizes of sturgeon observed, will provide information on whether or not the dam may be a signigicant barrier for the species.