Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon

St. Louis, Missouri, 11-13 January 2005

23.  POPULATION ABUNDANCE AND SIZE CHARACTERISTICS OF PALLID STURGEON FROM THE OLD RIVER CONTROL COMPLEX, LOUISIANA

Bobby C. Reed, Louisiana Department of Wildlife and Fisheries, 1213 North Lakeshore Drive, Lake Charles, LA 70601; Phone 337-491-2577; FAX 337-491-2009; breed@wlf.louisiana.gov

Jan C. Dean, Natchitoches National Fish Hatchery, 615 South Drive, Natchitoches, LA 71457: Phone 318-352-5324; FAX 318-352-8082; jan_dean@fws.gov

Pallid sturgeon Scaphirhynchus albus, were state protected in Louisiana from all fishing exploitation beginning May 1990, and listed as a federally endangered species by the USFWS in October of 1990.  Since their discovery below the Old River Structure Complex (ORCC) in 1991, the sturgeon population has been sampled almost annually through 2004.  The ORCC includes two U.S. Army Corps of Engineer water control structures which can be opened to release water from the Mississippi River through an outflow channel to the Atchafalaya River and eventually to the Gulf of Mexico.  The Atchafalaya River is the primary distributary for the Mississippi River, and the ORCC is the main control point for these water releases.  The greater ORCC area also includes a hydroelectric plant and a lock for barge traffic between the Mississippi, Red and Atchafalaya rivers.  Thus, the ORCC pallid sturgeon population is an open population.

Over 340 pallids have been taxonomically identified during this time period, with most being measured, marked and released unharmed.  Over this same time period over 550 pallid X shovelnose hybrids have also been identified, indicating hybridization of the two species in the lower basin is more widespread than previously thought.  Examination of the pallid population size structure reveals that the southern population is reproducing and that recruitment is occurring on a regular basis.  While some age information is available, southern pallids are smaller in size than their northern counterparts, averaging 841 mm FL and 2683 grams in wt.  While sampling has been somewhat consistent since 1997, only 13 pallids have been recaptured.