Green sturgeon life history research and monitoring, Sacramento River 

Starting in 2016, we expanded our juvenile green sturgeon monitoring work in an effort to learn basic life history information on this threatened population. This includes trawling near the bottom of the river to capture fish of sufficient size for micro-acoustic tagging. Current efforts include collaborative research on juvenile green sturgeon in-river habitat use and migration, to determine entry timing and cues to the Sacramento-San Joaquin River Delta.

Red Bluff is actively working with the National Marine Fisheries Service, the Army Corps of Engineers and others using Juvenile Salmon Acoustic Telemetry System technology to gather habitat use and migration data. Data from tagged individuals can be accessed through the National Oceanic and Atmospheric Administration's CalFishTrack website.

The Red Bluff Fish and Wildlife Office established a green sturgeon research and monitoring program centered on the Red Bluff Diversion Dam in 2001. Sampling for green sturgeon eggs to determine spawning locations and sampling of larvae to determine habitat use and drift characteristics was originally funded by a grant through CALFED.

Sampling was conducted in the spring and summer of 2001, but the project was then discontinued. The primary results of that project were that green sturgeon eggs were found immediately below Red Bluff Diversion Dam and a single larvae was found several kilometers upstream of the dam, indicating spawning occurred both above and below the dam. It was noted that the dam created an impassable barrier to late arriving adult spawners.

In 2006, the Southern Distinct Population Segment of the North American Green Sturgeon was first listed as threatened under the federal Endangered Species Act. This listing renewed concerns over the impacts of Red Bluff Diversion Dam and renewed interest in determining life-history information of the only known spawning population in the area of the dam.

Coordination with the U.S. Bureau of Reclamation and the University of California, Davis, resulted in renewed efforts to initiate studies on the adult spawning population. From this coordination, it was determined that Red Bluff would reinitiate the egg and larval studies for a period of three years, from 2008 through 2010, and use acoustic telemetry data provided by the Bureau and the University to guide the efforts.

Sampling for green sturgeon eggs began in the spring of 2008 using a variety of substrate sampling devices. Real-time acoustic data were used to determine sampling start dates and to increase the precision of sampling locations. With little knowledge of exact spawning locations, a sampling regime of upstream, within and below known sturgeon holding areas was tested. It was determined that green sturgeon eggs were found exclusively in the “within pool” areas. The efforts have been and continue to be further refined as data have been collected from the 2009 and 2010 seasons with multiple spawning sites confirmed above, at and below the dam.

Sampling for drifting larvae near the bottom of the river using a net also commenced in the spring of 2008 at four sampling locations centered on the dam (two above and two below) following the sampling of green sturgeon eggs. All sampling locations were experimentally sampled in a pilot effort to see if trends or patterns existed on nocturnal distribution patterns to better guide future sampling efforts with limited resources. Survey work in 2012 included a pilot effort to sample juvenile green sturgeon.

For results of these studies, please email caryl_brown@fws.gov.