Acipenser oxyrinchus desotoi
About the Species
The Gulf sturgeon is a sub-species of the Atlantic sturgeon that can be found from Lake Pontchartrain and the Pearl River system in Louisiana and Mississippi to the Suwannee River in Florida. Hatched in the freshwater of rivers, Gulf sturgeon head out to sea as juveniles, and return to the rivers to over summer or spawn (lay eggs) when they reach adulthood.
The Gulf sturgeon has five rows of bony plates known as scutes that run along its body and a snout with four barbels (slender, whisker-like, soft tissue projections) in front of its mouth. Similar to sharks, Gulf sturgeon have tails where one side, or lobe, is larger than the other. All of these features give the fish its unique look.
In 1991, Gulf sturgeon were listed as threatened under the Endangered Species Act after their population was greatly reduced or eliminated throughout much of their range because of overfishing, dam construction, and habitat degradation. NOAA Fisheries and the U.S. Fish and Wildlife Service jointly manage and protect Gulf sturgeon.
A variety of survey methods and gear have been used to estimate Gulf Sturgeon abundance both within and across rivers. Some surveys regularly target only particular geographic areas within a river (e.g., a summer holding area) or specific age-classes making it difficult to assess Gulf sturgeon abundance at both riverine and species scales.. Therefore, surveys over time within and across rivers are not easily comparable.
Gulf sturgeon can grow to be 9 feet in length and weigh over 300 pounds. Females grow larger than males. They are bluish-black or olive brown on their dorsal side (or back), with paler sides and a white belly. They have five major rows of dermal "scutes,” or thorny plates along the length of their body.
Behavior and Diet
Gulf sturgeon spawn in rivers in the spring and fall and spend the summer months in the riverine habitat between the upstream spawning areas (where they lay their eggs) and the estuary (mixed-salinity area where a river meets the sea). Subadults and adults do not feed when they are in the river. In the fall, both subadults and adults move into estuarine waters and feed extensively. Adults will move into marine waters in the winter, but younger size classes remain in the estuarine and freshwater habitats until about age 2 or 3.
Gulf sturgeon are described as opportunistic and indiscriminate benthivores (bottom-feeders) that change their diets and foraging areas during different life stages. Gulf sturgeon use specialized snout parts that look like whiskers, called barbels, to feel around on the bottom for food that includes invertebrates such as crustaceans, worms, and mollusks.
Where They Live
Historically, Gulf sturgeon occurred from the Mississippi River east to Tampa Bay. Sporadic occurrences were recorded as far west as the Rio Grande River in Texas and Mexico, and to Florida Bay in the east. Their present range extends from Lake Pontchartrain and the Pearl River system in Louisiana and Mississippi respectively, east to the Suwannee River in Florida. Based on current data, populations continue to reproduce in seven river systems (Pearl, Pascagoula, Escambia, Yellow/Blackwater, Choctawhatchee, Apalachicola, and Suwannee rivers). In addition to the seven spawning riverine populations, Gulf sturgeon are also known to inhabit the Mobile, and Ochlocknee rivers.
Lifespan & Reproduction
Gulf sturgeon live 20 to 25 years on average, but they may live up to 50 years.
Gulf sturgeon move from the Gulf of Mexico into coastal rivers in early spring (March to May). Spawning occurs in the upper reaches of rivers in the spring when the water temperature is around 59°F to 68°F. Fertilization is external. Females deposit their eggs on the river bottom and males fertilize them. Gulf sturgeon eggs sink and adhere to the bottom, and they vary in color from gray to brown to black. After hatching, juvenile Gulf sturgeon generally disperse downstream of spawning sites, though some may travel upstream as well, and move into estuarine feeding areas for the winter months.
In the fall, movement from rivers into estuaries and associated bays begins in September and continues through November. Most subadult and adult Gulf sturgeon spend the cool winter months (October/November to March/ April) in bays, estuaries, and the nearshore Gulf of Mexico. Tagged fish have been found in well-oxygenated shallow water areas that support burrowing macro invertebrates. These areas may include shallow shoals (5 to 7 feet), deep holes near passes, unvegetated sand habitats such as sandbars, and intertidal and subtidal energy zones.
Pollution and contamination from industrial, agricultural, and municipal activities is believed to cause a variety of physical, behavioral, and physiological impacts to sturgeon worldwide. Specific impacts include muscle atrophy; abnormal gonad, sperm, egg, and larval development; organ mutations; tumors; and disruption of hormone production. Chemicals and metals often settle to the river bottom and are later incorporated into the food web as they are consumed by benthic feeders, such as sturgeon or macroinvertebrates.
Dredging activities can significantly impact aquatic ecosystems by directly removing or burying organisms, causing turbidity/siltation effects, resuspending contaminants, making noise and causing disturbance, altering the hydrodynamic regime and physical habitat, and destroying riparian habitat. Dredging operations may also destroy benthic feeding areas, disrupt spawning migrations, inadvertently injure or kill individual fish by suction into the draghead, and resuspend fine sediments causing siltation over required substrate in spawning habitat. Because Gulf sturgeon are benthic omnivores, the modification of the benthos affects the quality, quantity, and availability of prey.
Dams significantly impact Gulf sturgeon by blocking passage to historical spawning habitats, which reduces the amount of available spawning habitat, where reproduction occurs, or entirely impedes access to it. The ongoing operations of these dams also affect downstream habitat, by altering flow and water quality.
Global climate change may lead to accelerated changes in Gulf sturgeon habitat through saltwater intrusion, changes in water temperature, increased frequency and intensity of hurricanes and red tides (and associated fish kills), exacerbation of the world’s largest dead zone where the Mississippi river meets the Gulf of Mexico, and extreme weather periods that could increase both the frequency and intensity of droughts and floods.
The following table provides the most recent abundance estimates reported in the 5-year review by river.
|River||Year of Data Collection||Abundance Estimate||Lower Bound 95% CI||Upper Bound 95% CI||Source|
|Suwannee||2007||14,000||Not Reported||Not Reported||Sulak 2008|
|Apalachicola||1991||144||83||205||Zehfuss et al. 1999|
|Choctawhatchee||2008||3,314||Not Reported||Not Reported||USFWS 2009|
|Yellow||2003 (fall)||911||550||1,550||Berg et al. 2007|
|Pascagoula||2000||216||124||429||Ross et al. 2001|
|Pearl||2001||430||323||605||Rogillio et al. 2001|
In the Spotlight
Gulf sturgeon are protected under the Endangered Species Act. Seven spawning populations have been identified (Pearl, Pascagoula, Escambia, Yellow, Choctowhatchee, Apalachicola, and Suwanee river populations). Various academic and governmental partners are conducting research on all seven populations.
Recovery Planning and Implementation
The short-term recovery objective for Gulf sturgeon is to prevent further reduction of existing wild populations. The long-term recovery objective is to establish population levels that would allow Gulf sturgeon to be delisted in discrete management units. Following delisting, a long-term fishery management objective is to establish self-sustaining populations that could withstand directed fishing pressure within discrete management units.
The Gulf Sturgeon Working Group identified several priorities for funding and research, the following studies have been implemented and are underway:
- Mapping and characterizing spawning habitat in the Pearl and Pascagoula rivers.
- Tracking juvenile seasonal movements in estuarine environments. Monitoring water quality to complement existing sonic tagging arrays.
- Continuing to maintain the Gulf sturgeon tagging database.
Species Recovery Contact
Joe Heublein, Species Recovery Coordinator, Southeast Region
Once a species is listed under the ESA, NOAA Fisheries evaluates and identifies whether any areas meet the definition of critical habitat. Those areas may be designated as critical habitat through a rulemaking process. The designation of an area as critical habitat does not create a closed area, marine protected area, refuge, wilderness reserve, preservation, or other conservation area; nor does the designation affect land ownership. Federal agencies that undertake, fund, or permit activities that may affect these designated critical habitat areas are required to consult with NOAA Fisheries to ensure that their actions do not adversely modify or destroy designated critical habitat.
In 2003, NOAA Fisheries 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. We designated these areas because they contain features that are essential for Gulf sturgeon survival, providing important spawning, feeding, and migratory habitats.
Co-Managing Gulf Sturgeon as an ESA-Listed Species
NOAA Fisheries and the U.S. FWS co-manage Gulf sturgeon. NOAA Fisheries supports conservation efforts and consults on activities that could impact this species.
The U.S. FWS works on mark/recapture research and telemetry tagging to evaluate Gulf sturgeon movements and hopefully gain better abundance estimates. In addition, they provide outreach to educate the public about this species.
Identifying Survey Protocols and Monitoring Procedures
NOAA Fisheries and the U.S. FWS organized and hosted a workshop in 2009 to identify survey protocols and monitoring procedures to fulfill the data needs of future assessments. The primary objective was to obtain reliable estimates of natural mortality and abundance throughout the Gulf sturgeon’s range. This multiyear survey and monitoring project facilitated these objectives by standardizing the data collection methodology and collecting critical data to assess the status of the Gulf sturgeon. In addition, the project was viewed as an opportunity to obtain other life history information. The project began in 2010. Because of its success and research partners’ willingness to continue these efforts, additional funding for this project has been secured over the last several years. The project continues to provide valuable insight into Gulf sturgeon behavior and habitat use, as well as necessary data to conduct mortality estimates and stock assessments in future years.
Restoring Habitats and Fish Passages
Sturgeon and other anadromous (migrating from rivers to oceans and back) fish, such as salmon, shad, and alewives, need access to freshwater habitat for spawning and rearing. Gulf sturgeon need to swim hundreds of miles through the oceans and rivers to reach their destination, but man-made barriers such as dams may block them from completing their journey. These barriers have seriously impacted Gulf sturgeon spawning runs. Removing outdated dams can greatly improve Gulf sturgeon access to historical habitats. NOAA Fisheries works with conservation organizations, energy companies, states, tribes and citizens to evaluate barriers and improve fish passage. Most barriers have the same general impact on fish—blocking migrations—but each requires a specific set of conservation actions.
Key Actions and Documents
NOAA Fisheries and the U.S. Fish and Wildlife Service co-manage Gulf sturgeon. We conduct various research activities on the biology, behavior, and ecology of this species. This research informs management decisions and enhances recovery efforts for the Gulf sturgeon.
Standardizing Data Collection
There is an ongoing multiyear survey and monitoring project to standardize data collection and collect critical data to assess the status of the Gulf sturgeon. In addition, the project provides an opportunity to obtain other life history information. Over the last several years, this research has provided valuable insight into Gulf sturgeon behavior and habitat use, as well as the necessary data to conduct mortality estimates and stock assessments in future years.
Other ongoing work includes the assessment of estuarine habitat-use patterns by juvenile Gulf sturgeon, as well as trends in juvenile sturgeon recruitment, growth, survival, genetics, and kinship across the range of the species.
Scientists use various tagging techniques to learn about the migration patterns of Gulf sturgeon and to identify important juvenile habitats. The types of tags generally used are floy-style dart tags, passive integrated transponder (PIT) tags, and acoustic tags (tags detected using sound). Tags such as PIT and dart tags allow other researchers to identify an individual fish when it is captured. Acoustic telemetry tags (tags that are detected with acoustic receivers) let researchers learn where Gulf sturgeon migrate, at what depths, and at what speeds.
Gulf sturgeon researchers take small fin clips from sturgeon they catch to better understand the genetic composition of all populations. Gulf sturgeon that are accidentally captured or killed in non-research-related projects can be identified to the river they were born in using information in their DNA (“genotype”). In other cases, researchers can take a tissue sample from sturgeon spawning (releasing or depositing eggs) or hatching in a particular river. After a laboratory processes the sample, the genetic information in that sample can be stored with other Gulf sturgeon genotypes to create baselines of the unique genotypes found for each spawning population. In the future, those baselines will allow sturgeon to be identified back to their natal river. Genetic variation (heterogeneity) within the population can also be used to estimate the minimum number of spawning adults that would have been required to generate that level of heterogeneity, which helps us learn more about where they come from and their family history.
Side Scan Sonar
Recently, side scan sonar in rivers has been used to approximate the number of large sturgeon (over 4 feet) that appear on the sonar image, but this approach is still being perfected. This is one of the most promising means of inexpensively estimating the abundance of sturgeon in a river at a given time.
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