Dissertations / Theses on the topic 'White sturgeon White sturgeon Caviar'

Harvesting sturgeon Acipenseridae when the ovarian follicles have the appropriate firmness and size is important for the caviar industry in order to produce a consistently uniform product and maximize caviar yield. Therefore, it is beneficial for the caviar industry to detect fish with atretic ovarian follicles prior to harvest, which can cause a decrease in caviar grade or complete loss of the product and to harvest fish at the correct stage of ovarian maturity to produce the highest quality and yield of caviar possible. The objectives of this study were to find a parameter that can detect early signs of ovarian follicular atresia by measuring blood plasma concentrations of sex steroids and determine if correlations exist among plasma sex steroid concentrations, morphological characteristics, and caviar yield and quality. To achieve the first objective, blood and ovarian follicles were collected repeatedly from 15 fish prior to and after inducing follicular atresia. Plasma testosterone (T) was the best indicator of the onset of atresia. Logistic regression models were used to illustrate how a threshold value of T can be determined to decrease the probability of harvesting white sturgeon with atretic ovaries. To achieve the second objective, biological samples (blood, ovarian follicles) and morphological measurements were collected from white sturgeon at caviar harvest (n = 20 per month) for five months. Analyses of parameters associated with caviar quality were limited because 92% of fish produced the same quality of caviar. Plasma E2 was correlated with caviar yield, caviar yield as a percent of body weight, and gonadosomatic index (GSI), whereas T was not correlated with either caviar yield or caviar yield as a percent of body weight. Ovarian fat varied greatly among individuals. Consequently, the ovarian stage associated with caviar yield could not be determined by measuring morphological parameters indicative of ovarian maturity. Post-hoc analyses were conducted to determine if parameters differed among ovarian fat categories. In the future, this study may benefit sturgeon conservation propagation programs by improving techniques for detection of ovarian atresia and offering a less-invasive method for estimating fecundity by utilizing the correlation between plasma E2 and GSI.

Considerable effort has been dedicated to restoring sturgeon habitat within dammed rivers. However, sedimentation causes long-term failure because interstitial voids provide critical habitat during early life-stages. Based on the premise that a better understanding of geomorphic processes will improve restoration design, this study characterizes flow and sediment transport dynamics through a white sturgeon spawning reach on the Nechako River, BC. An extensive dataset was collected throughout the 2015 flood. Bedload transport was sampled on 36 days with flows ranging from 44 m³/s to 656 m³/s. During a high flow of 525 m³/s, channel bathymetry and water surface elevation were surveyed and velocity profiles were collected across 9 transects. Banklines, bars and island topography were later surveyed during low flow. Sediment transport into the reach was positively related with discharge. This relation was non-linear and transport rates increased rapidly once flows exceeded 400 m³/s. The relation weakened with downstream distance and sediment transport peaked progressively later throughout the year. No relation was observed at the downstream end of the reach, where transport rates remained low and constant relative to upstream. Sediment was primarily transported through secondary channels conveying a disproportionate amount of sediment compared to flow. Within the single-thread channel, the locations conveying the greatest amount of sediment remained spatially consistent over time. Hydrodynamic modelling indicates the Burrard Ave. Bridge causes backwatering once discharge exceed 225-275 m³/s. Velocity, shear stress and transport capacity at the downstream end of the reach do not increase with discharge because of the backwatering and the expansion in channel width through the island complex. The locations of maximum shear stress and transport capacity shift upstream with increasing discharge, but shear stress does not exceed 23 N/m² for flows up to 775 m³/s. The fluvial dynamics within the spawning reach create challenges and opportunities for habitat restoration. Backwatering is problematic because it causes mid-reach deposition during high flows and limits shear stress magnitude over the downstream spawning substrate. Meanwhile, the presence of sediment transport pathways through secondary channels and within the mainstem can be used to site restoration projects in areas apt to maintain suitable habitat.
Arts, Faculty of
Geography, Department of
Graduate

White sturgeon populations in North America have dramatically decreased because of the commercial demand for caviar in the past and anthropogenic activities in the present. To conserve white sturgeon, recovery planning is required to ensure that the fish are self-sustaining through natural reproduction. However, little is known about many important aspects of white sturgeon biology, including their ability to detect and respond to alarm cues, the goal of this thesis. My results show that larval white sturgeon possess epidermal club cells, which in other fish are known to contain alarm cues. I investigated the effect of exposure to whole body extracts (WBE) of conspecifics (which contain the epidermal cells) on olfaction, through the use of electro-olfactogram (EOG), and investigated the effect of WBE exposure on behavioural responses and whole body cortisol levels in ~20 day post hatch white sturgeon larvae. The fish larvae showed alarm behaviors, such as avoidance, dashing, and freezing when exposed to WBE. In WBE treatment, the fish also increased whole body cortisol levels that are known as an indicator of stress. This thesis not only provides information on fundamental aspects of white sturgeon biology, but also may help fisheries management to understand how alarm substances are perceived in hatchery-reared naïve white sturgeon larvae.
Science, Faculty of
Zoology, Department of
Graduate

Through investigations conducted at the organismal, tissue and cellular levels, this thesis provides clear evidence that the white sturgeon, Acipenser transmontanus, is among the most CO₂ tolerant of all fishes investigated to date. During moderate increases in water CO₂ tension (PCO₂) (≤ 15 mm Hg PCO₂, hypercarbia), white sturgeon exhibited changes in gill morphology and restored blood pH (pHe) through net HCO₃⁻/Cl⁻, a process observed in most fishes (Chapter 3). At CO₂ tensions lethal to other fishes (≥ 22.5 mm Hg PCO₂), white sturgeon completely protected intracellular pH (pHi) of the heart, liver, brain and white muscle (termed preferential pHi regulation), despite a large reduction in pHe (up to 1 pH unit) (Chapter 3, 4). Tissue pHi regulation was activated in heart within minutes of the onset of hypercarbia (measured via NMR, Chapter 5), and completely protected pHi in this tissue even during exposure to potentially lethal CO₂ levels (i.e., 90 mm Hg PCO₂). In hearts examined in situ, maximum cardiac performance was well defended and associated with partial pHi compensation in ventricles (which exhibited only ~40% of predicted acidosis). Preferential pHi regulation was not associated with large increases in metabolic costs, as during exposure to severe hypercarbia (~45 mm Hg PCO₂), heart [ATP] and [CrP] had recovered to pre-exposure levels within 90 min, and whole animal was decreased (30%) when pHi was completely protected. Preferential pHi regulation of this magnitude and rapidity has not been documented before in any vertebrate in response to hypercarbia and represents a novel pattern of acid-base regulation among fishes. White sturgeon represent the first exclusively water-breathing fish to exhibit preferential pHi regulation during hypercarbia. Furthermore, white sturgeon are the most basal vertebrate to demonstrate complete pHi protection during severe pHe depression. As sturgeon may retain ancestral characteristics, I propose that preferential pHi regulation is the basis for enhanced CO₂ tolerance in other tolerant Osteichthyan fishes, and first arose in association with ionoregulatory and respiratory challenges experienced during freshwater invasion in the vertebrate lineage.

White sturgeon are a conservation concern throughout their range, and three populations in Canada are experiencing nearly zero recruitment. While the presence of large dams on the Nechako, upper Columbia and Kootenay rivers suggests a causal relationship between flow regulation and recruitment failure, persistent uncertainty regarding the species’ biology and its interaction with anthropogenic habitat change limits the understanding of the causal mechanisms of recruitment failure. Recruitment failure causation in the Nechako and upper Columbia rivers was evaluated by comparing hindcasted recruitment with historical environmental changes. For the Nechako River population, recruitment failure coincided with substrate changes at a known spawning site; these changes were identified based on air photos and changes in river bed elevation. Evaluation of the upper Columbia River population considered the effects of multiple dams and other anthropogenic impacts, as well as the effects of sturgeon aging error and population structure. Eleven recruitment failure hypotheses were evaluated based on fifteen criteria, including stock specific temporal and spatial patterns of recruitment decline. Estimated timing of stock-specific recruitment declines was also compared with reach and watershed scale environmental changes and site-specific habitat changes. For both analyses, substrate change at spawning sites was identified as the likely cause of recruitment failure. Embryos and yolksac larvae are expected to be the primary life stages affected in both cases. Laboratory and field enclosure studies assessed the effects of substrate on drift, hiding and survival of yolksac larvae. Contrary to many prior investigations, interstitial hiding was the predominant behaviour in laboratory studies in the presence of suitable interstitial habitat, and both drift and predation by sculpins (Cottus spp.) increased when interstitial habitat was unavailable. Rapid and sustained hiding by yolksac larvae and increased survival all suggest that hiding predominantly occurs in the vicinity of spawning habitat. Collectively my results indicate that recruitment failure results from increased early life history mortality in response to substrate changes at spawning sites. Increased survival of yolksac larvae in response to gravel augmentation in field studies suggests that larger-scale substrate restoration at spawning sites provides a habitat based approach for recruitment restoration.

The sharp decline of Fraser River white sturgeon (Acipenser transmontanus) in the late 1800s was the result of large catches in response to a market demand for caviar and smoked sturgeon. After a long period of indifference, the British Columbian public became concerned with the lack of white sturgeon information and probable large stock decline during the summer of 1993 with the discovery of several large white sturgeon carcasses. In September of 1994, a "catch and release" policy was implemented and met with mixed reactions. Nevertheless, uncertainties about stock reactions to harvest favoured the current cautious approach to limit retention. The objectives of this thesis are to: clarify objectives and struucture strategies for white sturgeon management; analyze uncertainty under these strategies in a stock harvest model; and discuss the role of uncertainty in management decisions and structure. It must be recognized that no perfect management solution exists. However, structuring fisheries management objectives and exploring uncertain stock reactions must be the first, crucial step to success. By simulating future events based on past stock reaction patterns, various white sturgeon harvest strategies and their ability to achieve management objectives is evaluated. This study focuses on how Fraser River white sturgeon might react under various harvest strategies designed to achieve management objectives by treating recruitment stochastically in a delay-difference model as unpredictable "states of nature." Results indicate that the probability of over harvest changes surprisingly little. This may help managers and stakeholders to assess their roles in the management process. Thus, uncertainty was quantified to show that the role of risk assessment in developing strategies to achieve long-term harvest objectives for Fraser River white sturgeon is important. While theoretical arguments are not too convincing, in practice, white sturgeon may be suitable for unusual harvest management initiatives such as individual quotas.

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.

Throughout North America populations of white sturgeon (Acipenser transmontanus) are threatened, in part due to poor annual recruitment. Definitive causes for this are not yet known, but the effects of contaminants are suspected to contribute. White sturgeon are exposed to a range of contaminants as they tend to inhabit industrialized river systems such as the Columbia and Fraser. White sturgeon are not commonly studied in ecotoxicology and their vulnerability as a species to contaminants of environmental concern is not well defined. To date, few exposure studies have been conducted with larvae, fry, and/or juveniles of this species; life stages often considered most susceptible to pollutants. Specifically, little work has been conducted to characterize effects of metals on white sturgeon. In the Upper Columbia River (UCR) a population of white sturgeon has been experiencing poor annual recruitment for over thirty years, and the effects of metal pollution have been hypothesized as a potential contributing factor. In particular, Teck Metals Ltd. (Teck) operates a metallurgical facility in Trail, BC, Canada that currently discharges processed effluent into the river and historically released other metal containing tailings such as slag. There are concerns that concentrations of trace-elements, such as copper, lead, cadmium, and zinc, associated with the effluent and/or slag, might have detrimental impacts on the surrounding ecosystem, including the local white sturgeon population. In 2006, a remedial investigation and feasibility study (RI/FS) was initiated in the UCR, under the oversight of the US EPA, and this project is contributing to the portion dedicated to the risk assessment of the exposure of white sturgeon to metals. The goals of this project were to develop information on toxicity of water, sediments and associated slag to help characterize sensitivity of white sturgeon to metals, and assess associated risks of metals on the population of white sturgeon in the UCR. Previous work conducted as part of a MSc degree, examined the effects of liquid effluent released by Teck on early life stages of white sturgeon. In addition, baseline information of toxicity due to sub-chronic exposure of early life stage sturgeon to copper, cadmium, and zinc, were developed. The thesis presented herein builds upon this previous work and has three major components to further characterize sensitivity of white sturgeon to metals and risk of exposure in the UCR. Specifically, a series of acute dose-response experiments were conducted with various early life stages of white sturgeon and resulting threshold values compared to water quality standards to assess protectiveness. Sensitivity of white sturgeon to metals was characterized by conducting parallel experiments with standard test species, such as rainbow trout (Oncorhynchus mykiss) and fathead minnow (Pimephales promelas), as well as parallel field exposures in UCR water to develop water effect ratios (WERs) and assess relative bioavailability. A second set of experiments investigated whether exposure to water downstream of the metal smelter in Trail, BC affected survival or growth of white sturgeon. Mobile laboratories were situated riverside upstream and downstream of the smelter and the effects of potential contaminants within UCR water to early life stage white sturgeon were investigated under chronic exposure conditions. The third set of experiments involved characterizing UCR sediment toxicity and potential effects to sturgeon. Results from this research indicate that early life stage white sturgeon are relatively sensitive to copper, cadmium, lead, and zinc in comparison to other fishes. Sturgeon were particularly sensitive to copper, especially during early life stage development when larvae are transitioning to exogenous food. Thresholds for effects of copper on early life stage white sturgeon (LC50’s ranged between 9 and 22 μg/L) bracket water quality criteria for the protection of aquatic life (7.9 μg/L ± 1.5). This result indicated that white sturgeon in the UCR might not be adequately protected. Environmentally relevant concentrations of metals, such as copper, found in water, sediment, or waters associated with sediment of the UCR, including pore water and overlying water, may approach or exceed water quality criteria and lethal concentration (LC) values for sturgeon. Results from the risk assessment portion of this project, however, indicated that contaminants in the water column downstream of the metal smelter at Trail did not likely affect survival of white sturgeon. Dilution of Teck effluent in the river is such that, at the major spawning site where early life stages of sturgeon are likely to be present and where the riverside experiments from the present project were conducted, there would be no toxicity expected. Contaminants associated with sediments in the UCR and their impact on survival of sturgeon is also of concern as early life stages inhabit benthic habitats, on surface sediments, or in interstitial space between stones. Analytical results from this project did indicate that UCR sediment downstream of the smelter facility were significantly greater (p < 0.01) in concentrations of trace-elements, such as copper, lead, cadmium, and zinc, relative to reference sites. However, survival of white sturgeon was not adversely affected following exposure to UCR sediments. This project provided valuable information to help assess potential causes for poor recruitment of white sturgeon in the Columbia River. Advancements were made in characterizing the effects of metals to white sturgeon. In particular, life stage-specific sensitivities were identified that could have a significant impact on current risk assessment approaches and the derivation of protective water quality standards. There are several hypotheses as to why the number of white sturgeon have been decreasing in the UCR over the last few decades, but as of yet, no definitive cause for poor recruitment has been identified. As more research is conducted, possible causes for recruitment failure can be eliminated. Based on results from this project, metals in the UCR do not appear to be contributing directly to decreased survival of early life stage sturgeon.

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

There is concern regarding exposure of aquatic organisms to chemicals that interfere with the endocrine system. Disruption of the endocrine system can lead to impacts on sexual development, altered hormone levels, intersex, and ultimately reproductive failure. While effects of endocrine disrupting chemicals (EDCs) on standard laboratory species have been subject of intense study, to this day there is a large gap in knowledge and a high degree of uncertainty regarding the sensitivity of wild fish species to these compounds. One of the main concerns with current toxicity testing approaches is that they require the use of a large number of live animals, particularly when working with native species. Therefore, the aim of this study was to develop in vitro tissue explant assays that would enable the assessment of the sensitivity of different wild fish species native to North America to the exposure with EDCs. Specifically, two in vitro assays were developed: 1) A liver explant assay to assess effects of EDCs that can interact with the estrogen receptor (environmental estrogens), and 2) a gonadal explant assay to assess effects of EDCs on sex-steroid production. The test species selected were northern pike (Esox lucius), walleye (Sander vitreus), and white sucker (Catostomus commersoni) that were sampled from Lake Diefenbaker, Saskatchewan, Canada, and white sturgeon (Acipenser transmontanus) that were randomly selected from an in house stock reared from eggs. Liver tissue was excised from male fishes and exposed for 24 h to a synthetic estrogen, 17α- ethinylestradiol (EE2). Transcript abundance of vitellogenin (VTG), estrogen receptor (ER) α and β in liver tissue were quantified using qPCR. Gonad tissue from both male and female were excised and exposed for 24 h to a model inducer (forskolin) and inhibitor (prochloraz) of steroidogenesis. 11-ketotestosterone (11-KT) and estradiol (E2) were quantified in media by use of ELISA. Exposure to EE2 resulted in a concentration dependent increase in VTG in all species, and an increase in ERα in northern pike. Walleye males showed the greatest sensitivity to EE2. Gonad tissues exposed to forskolin showed a concentration dependent increase in 11-KT and E2. Exposure to prochloraz resulted in a decrease of 11-KTand E2. Male and female white sucker showed greatest sensitivity to forskolin, while male and female walleye showed greatest sensitivity to prochloraz. The seasonal time point during which gonad explants were excised and exposed had an impact on the potency and magnitude of response, resulting in a seasonal effect on sensitivity. Also, gonad explants from these species were found to have greater sensitivity than responses previously reported for in vitro explants of other fish species such as the fathead minnow (Pimephales promelas), and stable cell lines currently used as screening applications to detect chemicals that might disrupt the endocrine system. Therefore, current approaches that use stable cell lines or tissue explants from standardized small bodied laboratory species might not be protective of some wild fish species. These tissue explants represent a promising approach to help understand species sensitivity to EDCs, and if appropriately validated, could be a powerful tool for chemical screening.