Geology topics

W. Todd Slack

Publications and source records attributed to W. Todd Slack.

4 recordsLinked to original sources

USGS2026

Identifying overwintering habitat of silver and bighead carp in the lower Mississippi River: Implications for harvesting and population reduction

A total of 41 sites along a 58 mi reach of the Lower Mississippi River (LMR) were surveyed during winter 2022 for invasive carp aggregation.* Sites consisting of scallops closest to the dike-vegetated bank interface with deeper, slow-moving water and consistent access back to the main channel were preferred. Carp avoided strong currents, and there was no trend in depth selection other than avoiding shallow (less than 20 ft) water. In January 2023, recreation-grade sonar (e.g., side-scan and down-imaging) surveys were conducted in the same reach of the LMR to demonstrate the technology and evaluate carp population size at sites with high abundances based on previous surveys. Fish density was estimated to be 32 fish/10,000 yd 3 (95% confidence interval [CI; 31–34]) using down-imaging software, which is the first estimate of assumed bigheaded carp density in the LMR. Additional fish collections are needed to confirm species composition and size abundance provided by sonar technology. Resurveying sites with high carp abundance over a range of river stages would be necessary to fully characterize habitat conditions, evaluate influence of river stage on occupancy duration, and continue to evaluate species composition and mass removal techniques as a management option in the Lower Mississippi River.

Louisiana, Mississippi↗

USGS2025

Long‐term effects of low‐drop grade control structures on channel evolution in the Yazoo River Basin

Channel incision is a widespread problem, especially in river basins that have an extensive history of channel alterations. Because channel incision causes large ecological and economic consequences, the prevention of continued migration of headcuts, defined as a steep change in stream gradient over a short reach, has been the focus of many stream engineering projects. Low-drop grade control structures (GCS) are a type of structure installed to halt the upstream movement of a headcut and were widely installed in the rivers and streams of the Yazoo River Basin in northern Mississippi. The goal of this study was to evaluate the long-term effects of these structures 30+ years post installation. To assess GCS effects on channel morphology, stream cross-section surveys were used to calculate Bank Height Ratio, Width-to-Depth Ratio, and Entrenchment Ratio, while point estimates made along each transect were used to calculate the average sediment size distribution for each of 30 sites. Analyses revealed that the GCS were successful in checking channel incision moving headward in the streams: sites upstream of the GCS were less incised and had greater accumulations of fine substrates compared to sites downstream and sites on streams lacking erosion control structures. Given the widespread use of GCS, these results can inform efforts aimed at managing channel incision.

Mississippi↗

USGS2017

Status of scientific knowledge, recovery progress, and future research directions for the Gulf Sturgeon, Acipenser oxyrinchus desotoi Vladykov, 1955

The Gulf Sturgeon, Acipenser oxyrinchus desotoi , is an anadromous species of Acipenseridae and native to North America. It currently inhabits and spawns in the upper reaches of seven natal rivers along the northern coast of the Gulf of Mexico from the Suwannee River, Florida, to the Pearl River, Louisiana, during spring to autumn. Next to the Alligator Gar (Atractosteus spatula) , the Gulf Sturgeon is currently the largest fish species occurring in U.S. Gulf Coast rivers, attaining a length of 2.35 m and weights exceeding 135 kg, but historically attained a substantially larger size. Historically, the spawning populations existed in additional rivers from which the species has been wholly or nearly extirpated, such as the Mobile and Ochlockonee rivers, and possibly the Rio Grande River. Most Gulf Sturgeon populations were decimated by unrestricted commercial fishing between 1895–1910. Subsequently most populations remained unrecovered or extirpated due to continued harvest until the 1970s–1980s, and the construction of dams blocking access to ancestral upriver spawning grounds. Late 20th Century harvest bans and net bans enacted by the several Gulf Coast states have stabilized several populations and enabled the Suwannee River population to rebound substantially and naturally. Hatchery supplementation has not been necessary in this regard to date. Sturgeon are resilient and adaptable fishes with a geological history of 150 million years. Research undertaken since the 1970s has addressed many aspects of Gulf Sturgeon life history, reproduction, migration, population biology, habitat requirements, and other aspects of species biology. However, many knowledge gaps remain, prominently including the life history of early developmental stages in the first year of life. Natural population recovery is evident for the Suwannee River population, but seems promising as well for at least four other populations. The Pascagoula and Pearl River populations face a challenging future due a combination of natural and anthropogenic factors. These two populations, and perhaps the Escambia River population, are particularly vulnerable to periodic mass mortality due to major stochastic events including hurricanes, flooding, hypoxia, and toxic spills. The present manuscript provides a comprehensive synthesis of knowledge regarding the Gulf Sturgeon at the organismal and population levels, identifying knowledge gaps as priorities for future research. Topics not treated in the present synthesis include morphology, internal biology, physiology, and endocrinology. Topics only briefly treated include parasites and diseases, contaminants, and sturgeon aquaculture.

Journal of Applied Ichthyology↗

USGS2007

Assessment and control of an invasive aquaculture species: An update on Nile tilapia ( Oreochromis niloticus ) in coastal Mississippi after Hurricane Katrina

We provide information about the effects of Hurricane Katrina on populations of an invasive fish, the Nile tilapia (Oreochromis niloticus) in southern Mississippi. By resampling areas surveyed before the storm, we attempted to determine whether the species expanded its range by moving with storm-related floods. Additionally, we used rotenone to eradicate individuals of this species at a hurricane-damaged aquaculture facility on the Mississippi coast. Although our survey was limited geographically, we did not find the species to occur beyond the aquaculture facility, other than in an adjacent bayou. Our rotenone treatment of the facility appeared effective with only a single O. niloticus being collected six weeks after the treatment. To reduce the spread of O. niloticus in the southeastern U.S., it is important to continue to control feral populations, work to eliminate vectors for dispersal, and continue monitoring their distribution.

Southeastern Fishes Council Proceedings↗