The lake sturgeon (Acipenser fulvescens), is a species with considerable ecological, social and economic value. Unfortunately, over-exploitation and habitat alteration have led to the collapse of lake sturgeon fisheries across North America. Based on conservation concerns, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) identified eight designatable units (DUs) among Canadian populations of lake sturgeon using the limited information available. These DUs are intended to represent taxonomically, genetically, geographically, or biogeographically distinct units below the species level. In this study, the genetic structuring among 20 lake sturgeon localities was examined using nine microsatellite loci. Lake sturgeon localities conformed to hierarchical partitioning of genetic diversity, with the greatest genetic divergence between localities in the Great Lakes and Hudson Bay drainages. Finally, minimal divergences among the current DUs warrant adjustment of lake sturgeon DU boundaries, to more appropriately reflect the distribution of genetic differentiation among lake sturgeon localities.

The lake sturgeon (Acipenser fulvescens), is a species with considerable ecological, social and economic value. Unfortunately, over-exploitation and habitat alteration have led to the collapse of lake sturgeon fisheries across North America. Based on conservation concerns, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) identified eight designatable units (DUs) among Canadian populations of lake sturgeon using the limited information available. These DUs are intended to represent taxonomically, genetically, geographically, or biogeographically distinct units below the species level. In this study, the genetic structuring among 20 lake sturgeon localities was examined using nine microsatellite loci. Lake sturgeon localities conformed to hierarchical partitioning of genetic diversity, with the greatest genetic divergence between localities in the Great Lakes and Hudson Bay drainages. Finally, minimal divergences among the current DUs warrant adjustment of lake sturgeon DU boundaries, to more appropriately reflect the distribution of genetic differentiation among lake sturgeon localities.

Pallid sturgeon (Scaphirhynchus albus) is a native North American fish that was listed as a federally endangered species in 1990 due to failure in spawning and recruitment, perhaps as a result of human modifications to their habitat. The upper Missouri River basin pallid sturgeon have been shown to be genetically distinct from other pallid sturgeon. Since there has been no natural recruitment in the upper Missouri River for several decades, perpetuation of this genetically distinct unit is reliant on propagation using remaining wild fish as broodstock. The expense associated with acquiring unique individuals from the remaining wild broodstock is causing wild collection to become a less viable option each year. It has been proposed that rearing progeny of wild broodstock fish in a hatchery setting as captive broodstock may be feasible alternative to wild collections. The genetic risks associated with the creation of a captive broodstock need to be investigated and a captive management plan needs to be developed prior to the implementation of a captive broodstock program. The relatedness values and the effective population size for the wild caught founders were determined by genotyping wild upper Missouri River pallid sturgeon at 16 previously developed microsatellite loci. The founding wild broodstock were shown to encompass an ample amount of genetic variation and a sufficiently large effective population size. The broodstock currently housed as Gavin's Point National Fish Hatchery can be exclusively used for the propagation of pallid sturgeon to be stocked in the upper Missouri River with the caveat that descendents from each wild fish will be spawned in the future and that the reproductive variance of the broodstock be controlled to maximize Ne and thus reduce inbreeding.

The purpose of this project was to develop inexpensive, standardized, and high throughput Single Nucleotide Polymorphism (SNP) markers that discriminate between pallid (Scaphirhynchus albus) and shovelnose (S. platorynchus) sturgeon for use as a larval identification tool. A total of 67 polymorphic sites was identified in DNA sequences from three genes: Recombination Activating Gene-1, Beta Actin, and Beta-2-Microglobulin. Allele frequencies from the 10 most variable SNPs were characterized for both pallid and shovelnose sturgeon in three geographically separated populations throughout the range of the pallid sturgeon. To create a standardized method of genotyping SNPs for larval pallid and shovelnose sturgeon, 5' nuclease allelic discrimination (TaqMan) assays were designed for two unlinked SNPs that exhibited the greatest allele frequency differences between species. A power analysis compared these SNP loci and their diagnostic power for species discrimination compared to sixteen microsatellite loci currently used for species discrimination (Schrey et al. 2007) One SNP locus was the most powerful marker for species identification in the upper and middle Missouri River. This study provides practical genetic tools for species discrimination between pallid and shovelnose that will facilitate understanding addressing questions that were previously too costly, labor intensive or technically challenging to answer.

Nuclear microsatellite DNA and mitochondrial DNA variation were examined in coho salmon (Oncorhynchus kisutch) and white sturgeon (Acipenser transmontanus) populations in order to address conservation issues in each species. In coho the goal was to examine genetic structure on a broad scale, in order to facilitate the conservation of genetic resources within the species. Coho salmon were widely sampled across their North American range. In white sturgeon the goal was to characterize population structure within the Fraser River, in order to identify biologically meaningful management units within that system. White sturgeon sampling was restricted to two watersheds (the Fraser and Columbia rivers), allowing much more thorough sampling than was done for coho. For both species, the use of mitochondrial and nuclear markers proved advantageous over examining either marker alone. The coho data revealed two levels of intraspecific variation, and gave the best indication to date regarding how genetic resources might be distributed within this species. The data is useful for protecting this species' ability to evolve. In contrast, the sturgeon data identified four regions within the Fraser River between which migration is limited. The sturgeon data, therefore, facilitate prevention of extirpation of local populations within the Fraser River. / Graduate

The habitat requirements of shovelnose sturgeon populations are unknown for the lower Mississippi River. Active acoustic telemetry was used to measure temporal variation in habitat use of shovelnose sturgeon and preference for depth, surface current velocity, and riverbed rugosity and slope by the population and within sandbar microhabitats. Shovelnose sturgeon occupied habitats differently throughout the year; and, within habitats, areas of moderate depth and surface current velocity and smooth riverbed were preferred. Within sandbars, environmental conditions did not differ from the surrounding environment, yet frequent aggregations of individuals in the lower portion of sandbars often in close proximity suggest habitat preference at a scale greater than the 5 ha measured. Results of this study provide information on seasonal habitat use patterns and methods that can be applied to a long-term dataset to identify the habitat requirements of shovelnose sturgeon.

Shovelnose Sturgeon patterns of movement are unknown for the lower Mississippi River. Active acoustic telemetry was used to determine how Shovelnose Sturgeon moved throughout a section of river and what influenced those movements. Distance to habitat type, depth, surface current velocity, river stage, change in river stage, river bottom slope, and temperature were investigated. Shovelnose Sturgeon were found not to have random or goal-oriented movements using a straightness index. Movement rate was influenced by river stage and surface current velocity. Habitat suitability changed with river stage and distance to habitat type supported a suite of delineated river features that Shovelnose Sturgeon use at different river stages. Results of this study provide movement and selection methods that can be applied to a long-term dataset to identify movement characteristics of Shovelnose Sturgeon in the lower Mississippi River.

Sturgeon are an ancient family of fish which have remained essentially unchanged for 200 million years, rendering them physiologically distinct from the more modern teleosts. Of the 26 known species of sturgeons all are likely endangered. North American populations have been declining steadily since the 1800s due to factors such as overharvesting, habitat alterations and increasing pollution. White sturgeon (Acipenser transmontanus), endemic to Western North America, are the largest freshwater fish on the continent. Protecting white sturgeon is of interest because nearly all Canadian populations are endangered and they are culturally and economically important. Factors such as great size, longevity, position in the food chain and benthic life style render white sturgeon particularly susceptible to bioaccumulation of toxicants. They are known to be among the most sensitive species to pollutants such as metal ions, dioxin-like compounds and endocrine disrupters. However, little is known about their susceptibility to other priority contaminants such as selenium (Se). Selenium, in its organic form selenomethionine (SeMet) has become a contaminant of particular concern as it is a known toxicant that efficiently bioaccumulates and biomagnifies in the food chain. It is also of interest as Se is an essential micronutrient that becomes toxic at only marginally greater than optimal doses. Current elevated concentrations of SeMet in white sturgeon prey, with predicted increases in anthropogenic releases, have made it a contaminant of concern for this species. It is hypothesized that increased releases of Se to aquatic environments have contributed in part to sturgeon declines; however, to date little is known about its specific effects on this species. Therefore, the purpose of the present study was to investigate the sensitivity of three year old white sturgeon to dietary SeMet and to link physiological effects to key molecular events of toxicity and to elucidate the mechanism of toxicity. Specifically, this thesis focused on oxidative stress in liver tissue as a hypothesized primary mechanism of toxicity. For 72 days sturgeon were given either a control diet of 1.4 µg Se/g feed or a diet spiked with SeMet (5.6, 22.4 or 104.4 µg Se/g feed dry mass). These doses corresponded to an uptake necessary for proper health, two environmentally relevant exposures, and a worst-case scenario for industrial Se release, respectively. A subsample of fish was taken at day 10 to investigate molecular endpoints. Within 10 days of exposure, pathological effects were observed in fish given the high dose. Occurrence of severe edema causing exophthalmos developed within 15, 23 and 52 days in high, medium and low dose group fish, respectively. There was a 54% and 22% occurrence of lethal effects in the high and medium dose groups, respectively. Se accumulated in a dose dependent manner and reached equilibrium in high dose fish after approximately 40 days. Growth, liver weight and hepatosomatic index were all significantly lower in the high dose group. Histology of 72 day liver samples showed a significant and dose dependent increase in melanomacrophage aggregates and decrease of energy stores and cell size. Food avoidance was also observed in sturgeon exposed to the high dose. To investigate oxidative stress, 10 day liver samples were tested for changes in gene expression coding for glutathione peroxidase (GPx), superoxide dismutase, catalase, glutathione S-transferase, apoptosis inducing factor and caspase 3, using real-time PCR. Only GPx was significantly induced. Day 72 liver samples were tested for the presence of lipid hydroperoxides but there were no significant differences between dose groups and controls, which shed doubt on oxidative stress being the main driver of toxicity. Taken together the data makes a strong case for the sensitivity of white sturgeon to Se accumulation and indicates a general suppression of health due to toxic levels of exposure. However, in contrast to other fish species exposed to Se, oxidative stress is not likely the main mechanism of toxicity in white sturgeon. Findings from the present study could be used for the risk assessment of sturgeon to anthropogenic Se in aquatic ecosystems.

Sturgeon species (family Acipenseridae) are threatened globally due to habitat destruction, pollution, and overfishing. The Atlantic sturgeon Acipenser oxyrinchus oxyrinchus was listed as a federally endangered species in 2012. Atlantic sturgeon have a complex life history that utilizes a wide range of habitats. Timing of life history varies in different areas requiring each population to be studied. Very little work has been published on Atlantic sturgeon reproduction in the James River, Virginia. To aid the recovery of James River Atlantic sturgeon, aspects of life history need to be addressed. To increase understanding of Atlantic sturgeon life history a length at age model was created to show population structure and age of sexual maturity. Telemetry experiments were conducted to determine what types of boats are likely to cause boat strike mortalities of adult fish during a spawning season. Morphometrics, sperm characteristics, and telemetry data were used to determine if Atlantic sturgeon have a fall spawning season. Strontium/calcium ratio analysis was conducted on Atlantic sturgeon fin spines to better understand migration patterns. Cortisol levels were examined in Atlantic sturgeon exposed to MS222, electronarcosis or no anesthetic 1 and 24 hr after a small incision mimicking tag implantation. I also determined the feasibility of using electronarcosis in the field and the effect of salinity on electronarcosis. The length at age data show male Atlantic sturgeon beco,e sexually mature at age 10 y and females around age 15 y. Telemetry data showed that deep draft ocean-cargo ships are most likely responsible for boat strike mortalities and there is a greater chance of Atlantic sturgeon being hit in the narrow portion of the river. Electronarcosis is an effective anesthetic and has various attributes that make it better suited for field applications then frequently used chemical anesthetics. The data generated from this research will help management produce effective recovery plans and create a safer research environment for both the fish and researcher.

Thesis (M.S.)--North Carolina State University, 2003. / Includes vita. Includes bibliographical references (p. 76-82).