Gulf Sturgeon

Gulf sturgeon

Occurrence and Description

The Gulf sturgeon, Acipenser oxyrinchus desotoi, is a large, primitive fish that has bony plates, or "scutes," rather than scales and a hard, extended snout. Gulf sturgeon have a toothless, vacuum-like mouth that projects from the lower surface of the head and four whisker-like barbels. The backbone is cartilaginous, like those of sharks, as are the five rows of external scutes that protect the head and top portion of the body. Sturgeon typically range in color from a light neutral color to dark brown and have a white under belly. Their caudal fin is heterocercal, meaning that their tail is distinctly asymmetrical with the upper lobe longer than the lower.

Adult Gulf sturgeon range from 4 feet (1-2.5 m) in length and weight up to 200 pounds. Females attain larger sizes than males. Gulf sturgeon can live for as long as 60 years, but their average lifespan is about 20-25 years.

GCRL Fisheries Ecology Technician Paul Grammer holding an adult Gulf sturgeon captured, tagged, and released on the Pascagoula River.
GCRL Fisheries Ecology Technician Paul Grammer holding an adult Gulf sturgeon captured, tagged, and released on the Pascagoula River. Click for larger image.

Sturgeons are an ancient group of fish dating back about 200 million years to the age of dinosaurs. Gulf sturgeon are a subspecies of Atlantic sturgeon, Acipenser oxyrinchus. It is very difficult to visually distinguish between the two. Worldwide there are 27 sturgeon species and two closely related species of paddlefish.

The Gulf sturgeon is a federally-listed threatened species (Federal Register 1991) and much of the river, bay and nearshore areas throughout its range are considered critical habitat in support of spawning,in-river holding, or feeding activities. (Critical habitat is a term used in the Endangered Species Act (ESA) to refer to specific geographic areas that are essential for the conservation of a threatened or endangered species and that may require special management and protection.) Catching, harming, or disturbing Gulf sturgeon is prohibited by federal and Mississippi regulations.

Gulf Sturgeon Range Map, source: NOAA Fisheries Office of Protected Resources.
Gulf Sturgeon Range Map, source: NOAA Fisheries Office of Protected Resources. Click for larger image.

Gulf sturgeon occur in drainages from the Suwannee River in Florida to the Pearl River on the boundary of Louisiana and Mississippi. They spawn in up river reaches during the early spring and young-of-the-year (YOY) spend 6–10 months feeding in the river as they migrate down stream. They appear in the estuaries in December through February.  Juveniles (< 6 years; except YOY) are believed to overwinter in the estuary.  In Mississippi, large sub-adult and adult Gulf sturgeon have been shown to overwinter in the Mississippi Sound, congregating near the passes between barrier islands. The estuaries provide a essential link in the life history of Gulf sturgeon, ranging from a travel corridor connecting vital spawning and summer in-river holding areas, to nearshore and offshore marine feeding areas.


Feeding and Diet

Gulf sturgeon are bottom feeders (supra-benthic cruisers), consuming primarily macro-invertebrates, including brachiopods, mollusks, amphipods, polychaete worms, and other crustaceans. They rely on their barbels to detect prey items.

Adult Gulf sturgeon feed almost exclusively in brackish or marine waters of the Gulf of Mexico and its estuaries. Recently, it has been determined that Gulf sturgeon do very little feeding while in riverine habitats during the summer. The adults feed heavily in the winter when they are in the Gulf of Mexico and experience a substantial weight gain, followed by a weight loss during the summer.

Life Cycle & Reproduction

Gulf sturgeon are anadromous as adults (>1250 mm or four feet fork length), meaning that they spend time in both saltwater and freshwater, like salmon. Adults migrate upriver from the Gulf of Mexico in the springtime to spawn, returning to their natal streams to spawn, again similar to salmon.

Female Gulf sturgeon reach sexual maturity at 8-17 years of age. Males mature slightly earlier, at 7-12 years of age. Gulf sturgeon eggs are sticky and sink to the bottom, where they adhere in clumps to snags, or outcroppings.

They spawn in freshwater and migrate into marine waters in the fall to forage and overwinter. Juvenile Gulf sturgeon (304-890 mm FL) stay in the river for about the first two to three years and then move to the estuary where they forage until they reach sub-adult sized (891-1250 mm FL or three to four feet). Then they move to the barrier islands to forage, generally between December and March.

Interesting Facts About Gulf Sturgeon

Jumping - All species of sturgeon will jump at times. Gulf sturgeon can jump six feet out of the water. The Gulf sturgeon is known to jump at two times during the year: in the rivers during July and August and early in the offshore feeding period. It is thought that they jump in order to communicate and maintain group cohesion. Read more in this National Geographic News article.

Sounds - During spawning, sturgeon make a noise similar to a creaky door hinge.

Name - The subspecies name of desotoi honors Hernando de Soto, the Spaniard who explored what is now the southeastern U.S. in the 16th century.

Population Trends

The total number of adult Gulf sturgeon is unknown. However, the population in the seven coastal rivers of the Gulf of Mexico inhabited by Gulf sturgeon is estimated at more than 15,000 adults. Of those rivers, the Suwannee River in Georgia and Florida supports the most viable subpopulation, estimated at more than 9,000 adults in the mid-2000s. The subpopulation estimate for mature Gulf sturgeon in the Choctawhatchee River in Alabama and Florida is about 3,000 fish. However, estimates for other rivers (Pearl, Pascagoula, Escambia, Yellow, and Apalachicola) average around 400.

Threats

Historic populations of Gulf sturgeon were greatly reduced by overfishing, for meat and roe, throughout most of the 20th century.

Current threats include the following.

Conservation and Recovery Efforts

On September 30, 1991, the Gulf sturgeon was listed as a threatened species under the Endangered Species Act. In 2003, the National Marine Fisheries Service and the U.S. Fish and Wildlife Service jointly designated Gulf Sturgeon critical habitat in 14 geographic areas from Florida to Louisiana, encompassing spawning rivers and adjacent estuarine areas. In 1995, a Recovery/Management Plan was published for the Gulf Sturgeon. All U.S. fisheries for the Gulf sturgeon have been closed. This species is also included on the International Union for Conservation of Nature Red List of Threatened Species.

Current Research

Jeanne-Marie Havrylkoff holding a juvenile Gulf sturgeon tagged (see black acoustic tag on dorsal fin & two external tags on each pectoral fin) at night.
Jeanne-Marie Havrylkoff holding a juvenile Gulf sturgeon tagged (see black acoustic tag on dorsal fin & two external tags on each pectoral fin) at night.

Since 2007, faculty and staff of GCRL's Fisheries Ecology Lab have worked closely with colleagues at the U.S. Army Corps of Engineers Engineer Research and Development Center (USACE-ERDC) in Vicksburg to study Gulf Sturgeon ecology and movements.  Currently, there are three joint projects: the Pascagoula River, the Gulfport Harbor Expansion Project, and Ship Island Restoration. Dr. Mark Peterson is principal investigator for all three projects. Todd Slack, from the USACE-ERDC, is co-PI on the Gulfport Harbor and Ship Island projects.

Pascagoula River Project

The Pascagoula River is the only large river in the lower 48 States that is not dammed or has sills on the main stream. Our longest running project is conducted on this beautiful and wild river. Our research has provided considerable data on Gulf Sturgeon movements and ecology.  We tag Gulf Sturgeon in the Pascagoula River as well as in the Pearl River system.

The project focuses on movements of juvenile and sub-adult Gulf sturgeon relative to spatial and temporal benthic resource density (food items) and seasonal changes in that benthic component.  Early results strongly suggest minimal use of the east river zone of the Pascagoula River which has been strongly altered by urbanization, dredging, and other human activities. The more natural west river zone shows much higher Gulf Sturgeon activity.

Map of the Pascagoula River system and Vemco telemetry arrays and benthic sampling stations.
Map of the Pascagoula River system and Vemco telemetry arrays and benthic sampling stations.

The Pascagoula River is the only fairly large river in the lower 48 States that is not dammed or has sills on the main stem (Dynesius and Nilsson (1994) and is thus a natural treasure for humankind and the terrestrial and aquatic resources therein (Jackson 2012).
The Pascagoula River is the only large river in the lower 48 States that is not dammed or has sills on the main stream (Dynesius and Nilsson (1994) and is thus a natural treasure for humankind and the terrestrial and aquatic resources therein (Jackson 2012).


Ship Island, Year Two

Buoy with acoustic listening device and datalogger used for tracking the movements of Gulf sturgeon.
Buoy with acoustic listening device and datalogger used for tracking the movements of Gulf sturgeon.

GCRL and other research groups track the movements of sturgeon in our area with the aid of acoustic tags implanted in the fish and listening buoys anchored in coastal waters. Each fish's acoustic tags emit a uniquely coded signal at regular time intervals. When a tagged fish passes within range of a buoy (roughly 1000 feet), a datalogger records the time and the tag identification code unique to that fish. One array of listening buoys is located at Ship Island and in the pass eastward to the tip of Horn Island. In 2012, a total of 21 Gulf sturgeon were tagged with acoustic tags in nearby rivers.

During the second year of our study, we recorded a total of 94,244 detections. (Not corrected for simultaneous detections from multiple buoys.)

Summary of Gulf Sturgeon detections through March 2013 at Ship Island study area.
Summary of Gulf sturgeon detections through March 2013 at Ship Island study area.

 

Gulfport Harbor Project, 2012-2013

GCRL researchers and others have been able to quantify movement and occupancy of all size classes of Gulf Sturgeon in these areas.  This information increases our understanding of the western population of Gulf Sturgeon and provides valuable data to local and federal agencies. The information is particularly valuable to the NOAA-NMFS Office of Species Protection and USFWS, who manage the conservation plan for this threatened species.

Summary of Gulf Sturgeon detections through March 2013 near Gulfport study area.
Summary of Gulf Sturgeon detections through March 2013 near Gulfport study area.

Resources and References

Photos

Jeanne-Marie Havrylkoff with subadult Gulf sturgeon from the Pascagoula River.
Jeanne-Marie Havrylkoff with subadult Gulf sturgeon from the Pascagoula River.

More photos from gulf sturgeon research at GCRL


Video

Web

Scientific References