PRESENTATION
Bobby C. Reed, Jan C. Dean, and Paul Hartfield breed@wlf.louisiana.gov
La Department of Wildlife and Fisheries, 1213 North Lakeshore Drive, Lake Charles, LA 70601
Natchitoches National Fish Hatchery, 615 South Drive, Natchitoches, LA 71457;
USFWS, Endangered Species Coordinator, 6578 Dogwood View Parkway, Jackson, MS 39213
Abstract
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 Control Complex (ORCC) in 1991, the sturgeon population has been sampled almost annually through 2007. 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.
About 650 pallid sturgeons have been taxonomically identified during this time period, with most being measured, marked and released unharmed. Over this same time period over 600 pallid X shovelnose hybrids have also been identified, indicating that hybridization of the two species in the lower basin is more widespread than previously thought. Examination of the pallid sturgeon 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. A total of 33 pallid sturgeons have been recaptured at the ORCS since 1991, with the latest population estimate for the area being 259 animals (95% C.I. = 170 to 355). In the spring of 2007, 24 pallids were implanted with sonic tags and are now being tracked, both actively and passively (stationary sentinel receivers) throughout the Atchafalaya River in order to determine seasonal movements/migration patterns. |