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White Sturgeon (Acipenser transmontanus), a species of concern in the San Francisco Estuary, is in relatively low abundance due to a variety of factors. The purpose of our study was to identify the estuarine habitat used by White Sturgeon to aid in the conservation and management of the species locally and across its range. We seasonally sampled sub-adult and adult White Sturgeon in the central estuary using setlines across a habitat gradient representative of three primary structural elements: shallow wetland channels (mean sample depth = 2 m), shallow open-water shoal (mean sample depth = 2 m), and deep open-water channel (mean sample depth = 7 m). We found that the shallow open-water shoal and deep open-water channel habitats were consistently occupied by White Sturgeon in spring, summer, and fall across highly variable water quality conditions, whereas the shallow wetland channel habitat was essentially unoccupied. We conclude that sub-adult and adult White Sturgeon inhabit estuaries in at least spring, summer, and fall and that small, shallow wetland channels are relatively unoccupied.

White Sturgeon (Acipenser transmontanus), a species of concern in the San Francisco Estuary, is in relatively low abundance due to a variety of factors. The purpose of our study was to identify the estuarine habitat used by White Sturgeon to aid in the conservation and management of the species locally and across its range. We seasonally sampled sub-adult and adult White Sturgeon in the central estuary using setlines across a habitat gradient representative of three primary structural elements: shallow wetland channels (mean sample depth = 2 m), shallow open-water shoal (mean sample depth = 2 m), and deep open-water channel (mean sample depth = 7 m). We found that the shallow open-water shoal and deep open-water channel habitats were consistently occupied by White Sturgeon in spring, summer, and fall across highly variable water quality conditions, whereas the shallow wetland channel habitat was essentially unoccupied. We conclude that sub-adult and adult White Sturgeon inhabit estuaries in at least spring, summer, and fall and that small, shallow wetland channels are relatively unoccupied.

An 8-week feeding trial was conducted to investigate the responses of juvenile white sturgeon (Acipenser transmontanus) to elevated dietary selenium (Se) based on the determination of the RNA/DNA ratio in muscle, heat shock protein 70 (Hsp70), and caspase-3/7 in muscle and/or liver tissues. Four semi-purified test diets were prepared by adding different levels of L-selenomethionine (0, 50, 100, and 200 mg/kg diet). The analytical determinations of total Se were 2.2, 19.7, 40.1, and 77.7 mg/kg diet. The sturgeon (initial body weight: 30 ± 2 g; mean ± SEM) were raised in indoor tanks provided with flow through freshwater (18-19 °C). There were three replicates for each dietary treatment with 25 fish per replicate. The liver and muscle tissues were collected at 4 and 8 weeks after feeding the test diets. A significant interaction between duration and levels of dietary Se exposures on RNA/DNA ratio in the muscle tissue was detected (P < 0.05). Although there was no significant main effect due to the duration of dietary Se exposures (i.e., 4 weeks versus 8 weeks) on muscle RNA/DNA ratio (P ≥ 0.05), the ratio was significantly decreased with increasing dietary Se levels. Significant main effects were caused by the duration and levels of dietary Se exposures on Hsp70 in both the muscle and liver tissues, with significant increases in Hsp70 due to a longer exposure (8 weeks) and higher levels (40.1 and 77.7 mg Se/kg diet) of dietary Se. The caspase-3/7 activity in the liver were significantly higher in fish fed the diets containing 40.1 and 77.7 mg Se/kg diet than those fed the other diets. The toxic thresholds of Se in the muscle were estimated to be 32.2 and 26.6 mg Se/kg for the depressed specific growth rate and the induced Hsp70 response in muscle, respectively. This result indicated that the Hsp70 response in muscle is a more sensitive biomarker than the SGR of sturgeon for evaluating Se toxicity in white sturgeon. Results of the current study suggest that a mechan

White sturgeon (Acipenser transmontanus) are the largest freshwater fish in North America and a species exposed to widespread fishing pressure. Despite the growing interest in recreational fishing for white sturgeon, little is known about the sublethal and lethal impacts of angling on released sturgeon. In summer (July 2014, mean water temperature 15.3°C) and winter (February 2015, mean water temperature 6.6°C), captive white sturgeon (n = 48) were exposed to a combination of exercise and air exposure as a method of simulating an angling event. After the stressor, sturgeon were assessed for a physiological stress response, and reflex impairments were quantified to determine overall fish vitality (i.e. capacity for survival). A physiological stress response occurred in all sturgeon exposed to a fishing-related stressor, with the magnitude of the resp

An 8-week feeding trial was conducted to investigate the responses of juvenile white sturgeon (Acipenser transmontanus) to elevated dietary selenium (Se) based on the determination of the RNA/DNA ratio in muscle, heat shock protein 70 (Hsp70), and caspase-3/7 in muscle and/or liver tissues. Four semi-purified test diets were prepared by adding different levels of L-selenomethionine (0, 50, 100, and 200 mg/kg diet). The analytical determinations of total Se were 2.2, 19.7, 40.1, and 77.7 mg/kg diet. The sturgeon (initial body weight: 30 ± 2 g; mean ± SEM) were raised in indoor tanks provided with flow through freshwater (18-19 °C). There were three replicates for each dietary treatment with 25 fish per replicate. The liver and muscle tissues were collected at 4 and 8 weeks after feeding the test diets. A significant interaction between duration and levels of dietary Se exposures on RNA/DNA ratio in the muscle tissue was detected (P < 0.05). Although there was no significant main effect due to the duration of dietary Se exposures (i.e., 4 weeks versus 8 weeks) on muscle RNA/DNA ratio (P ≥ 0.05), the ratio was significantly decreased with increasing dietary Se levels. Significant main effects were caused by the duration and levels of dietary Se exposures on Hsp70 in both the muscle and liver tissues, with significant increases in Hsp70 due to a longer exposure (8 weeks) and higher levels (40.1 and 77.7 mg Se/kg diet) of dietary Se. The caspase-3/7 activity in the liver were significantly higher in fish fed the diets containing 40.1 and 77.7 mg Se/kg diet than those fed the other diets. The toxic thresholds of Se in the muscle were estimated to be 32.2 and 26.6 mg Se/kg for the depressed specific growth rate and the induced Hsp70 response in muscle, respectively. This result indicated that the Hsp70 response in muscle is a more sensitive biomarker than the SGR of sturgeon for ev

The goal of a day-long symposium on March 3, 2015, Sturgeon in the Sacramento–San Joaquin Watershed: New Insights to Support Conservation and Management, was to present new information about the physiology, behavior, and ecology of the green (Acipenser medirostris) and white sturgeon (Acipenser transmontanus) to help guide enhanced management and conservation efforts within the Sacramento–San Joaquin watershed. This symposium identified current unknowns and highlighted new electronic tracking technologies and physiological techniques to address these knowledge gaps. A number of presentations, each reviewing ongoing research on the two species, was followed by a round-table discussion, in which each of the participants was asked to share recom-mendations for future research on sturgeon in the watershed. This article presents an in-depth review of the scientific information presented at the sympo-sium with a summary of recommendations for future research.

The goal of a day-long symposium on March 3, 2015, Sturgeon in the Sacramento–San Joaquin Watershed: New Insights to Support Conservation and Management, was to present new information about the physiology, behavior, and ecology of the green (Acipenser medirostris) and white sturgeon (Acipenser transmontanus) to help guide enhanced management and conservation efforts within the Sacramento–San Joaquin watershed. This symposium identified current unknowns and highlighted new electronic tracking technologies and physiological techniques to address these knowledge gaps. A number of presentations, each reviewing ongoing research on the two species, was followed by a round-table discussion, in which each of the participants was asked to share recom-mendations for future research on sturgeon in the watershed. This article presents an in-depth review of the scientific information presented at the sympo-sium with a summary of recommendations for future research.

The goal of a day-long symposium on March 3, 2015, Sturgeon in the Sacramento–San Joaquin Watershed: New Insights to Support Conservation and Management, was to present new information about the physiology, behavior, and ecology of the green (Acipenser medirostris) and white sturgeon (Acipenser transmontanus) to help guide enhanced management and conservation efforts within the Sacramento–San Joaquin watershed. This symposium identified current unknowns and highlighted new electronic tracking technologies and physiological techniques to address these knowledge gaps. A number of presentations, each reviewing ongoing research on the two species, was followed by a round-table discussion, in which each of the participants was asked to share recommendations for future research on sturgeon in the watershed. This article presents an in-depth review of the scientific information presented at the symposium with a summary of recommendations for future research.

The application of genetic markers to investigate evolutionary and ecological questions about white sturgeon, Acipenser transmontanus, has been limited due to the species’ highly duplicated nuclear genome. Here, polysomic microsatellite markers were used to 1) examine the ancestral level of genome duplication in white sturgeon, 2) examine genetic diversity and patterns of population structure within and among drainages across the species’ range, and 3) provide genetic monitoring for a conservation aquaculture program sustaining an endangered white sturgeon population. In the first chapter, we followed the inheritance of eight microsatellite markers in 15 families of white sturgeon from a commercial caviar farm to determine whether white sturgeon (~250 chromosomes) should be classified as tetraploid or octoploid. The eight microsatellite loci were detected predominantly in four or eight copies, with one locus observed in >8 copies. Numbers of alleles per locus, patterns of allele transmission, and inference of gene copy number in parents suggested that white sturgeon should be considered ancient octoploids. The discovery of dodecaploid parents and their decaploid offspring in the farm population, confirmed by flow cytometry analysis, indicated that some aspect of sturgeon aquaculture was inducing spontaneous autopolyploidy in white sturgeon.Next, microsatellite markers were applied to examine white sturgeon population structure across the species’ range. Population assignment testing was used to determine the origin of white sturgeon sampled in non-natal estuaries, or those not containing a spawning population, to evaluate marine dispersal behavior. The Sacramento-San Joaquin River system was found to contain a single white sturgeon population while the8Fraser River exhibited a hierarchical pattern of population structure. Strong levels of genetic divergence were detected above and below a natural barrier, Hells Gate, and fine-scale population substructure was ide

The application of genetic markers to investigate evolutionary and ecological questions about white sturgeon, Acipenser transmontanus, has been limited due to the species’ highly duplicated nuclear genome. Here, polysomic microsatellite markers were used to 1) examine the ancestral level of genome duplication in white sturgeon, 2) examine genetic diversity and patterns of population structure within and among drainages across the species’ range, and 3) provide genetic monitoring for a conservation aquaculture program sustaining an endangered white sturgeon population. In the first chapter, we followed the inheritance of eight microsatellite markers in 15 families of white sturgeon from a commercial caviar farm to determine whether white sturgeon (~250 chromosomes) should be classified as tetraploid or octoploid. The eight microsatellite loci were detected predominantly in four or eight copies, with one locus observed in >8 copies. Numbers of alleles per locus, patterns of allele transmission, and inference of gene copy number in parents suggested that white sturgeon should be considered ancient octoploids. The discovery of dodecaploid parents and their decaploid offspring in the farm population, confirmed by flow cytometry analysis, indicated that some aspect of sturgeon aquaculture was inducing spontaneous autopolyploidy in white sturgeon.Next, microsatellite markers were applied to examine white sturgeon population structure across the species’ range. Population assignment testing was used to determine the origin of white sturgeon sampled in non-natal estuaries, or those not containing a spawning population, to evaluate marine dispersal behavior. The Sacramento-San Joaquin River system was found to contain a single white sturgeon population while the8Fraser River exhibited a hierarchical pattern of population structure. Strong levels of genetic divergence were detected above and below a natural barrier, Hells Gate, and fine-scale population substructure was ide

Vitellogenin (Vg), the estrogen inducible protein precursor to egg yolk, serves as an indicator of exposure to estrogen mimicking environmental contaminants. Vg was isolated by size exclusion and ion exchange chromatography from plasma of California halibut (Paralichthys californicus) treated with estrogen. MALDI TOF mass spectrometry (MS) analysis resulted in a molecular mass of 188 kDa. MS/MS de novo sequencing provided evidence that California halibut has more than one form of Vg. Similar analysis on white sturgeon (Acipenser transmontamus) Vg did not reveal adequate evidence to suggest that sturgeon has more than one Vg. The potential of using other MS methods to understand the structure and function of Vg are discussed.An ELISA for measurement of California halibut plasma Vg was optimized and validated using a commercially available antibody developed for another flatfish species, turbot. Inclusion of overnight preincubation was critical for low detection limits. Increasing the amount of Tween-20 to 0.05% in buffers was most effective for improving recoveries of spiked plasma samples. At the IC50, the average recovery of spiked plasma samples was 104% and the interplate CV was 12%. The working range of the assay was 33-1000 ng/mL, while the detection limit in a plasma sample is 2.2 µg/mL. The response to the model compounds 17beta-estradiol and/j-nonylphenol show that this is a suitable model for further studies of estrogen mimicking contaminants.White sturgeon are native to the Sacramento River and subject to agricultural, municipal and industrial waste water effluents that likely contain different classes of endocrine-disrupting contaminants. Reductions in 17beta-estradiol-induced vitellogenin levels were observed in white sturgeon co-injected with beta-naphthoflavone (BNF, 50 mg/kg), an Ah receptor agonist. The inhibition was maximal when the compounds were injected simultaneously versus prior treatment offish with BNF. This timing of the effect compared to

Vitellogenin (Vg), the estrogen inducible protein precursor to egg yolk, serves as an indicator of exposure to estrogen mimicking environmental contaminants. Vg was isolated by size exclusion and ion exchange chromatography from plasma of California halibut (Paralichthys californicus) treated with estrogen. MALDI TOF mass spectrometry (MS) analysis resulted in a molecular mass of 188 kDa. MS/MS de novo sequencing provided evidence that California halibut has more than one form of Vg. Similar analysis on white sturgeon (Acipenser transmontamus) Vg did not reveal adequate evidence to suggest that sturgeon has more than one Vg. The potential of using other MS methods to understand the structure and function of Vg are discussed.An ELISA for measurement of California halibut plasma Vg was optimized and validated using a commercially available antibody developed for another flatfish species, turbot. Inclusion of overnight preincubation was critical for low detection limits. Increasing the amount of Tween-20 to 0.05% in buffers was most effective for improving recoveries of spiked plasma samples. At the IC50, the average recovery of spiked plasma samples was 104% and the interplate CV was 12%. The working range of the assay was 33-1000 ng/mL, while the detection limit in a plasma sample is 2.2 µg/mL. The response to the model compounds 17beta-estradiol and/j-nonylphenol show that this is a suitable model for further studies of estrogen mimicking contaminants.White sturgeon are native to the Sacramento River and subject to agricultural, municipal and industrial waste water effluents that likely contain different classes of endocrine-disrupting contaminants. Reductions in 17beta-estradiol-induced vitellogenin levels were observed in white sturgeon co-injected with beta-naphthoflavone (BNF, 50 mg/kg), an Ah receptor agonist. The inhibition was maximal when the compounds were injected simultaneously versus prior treatment offish with BNF. This timing of the effect compared to

An 8-week growth trial was conducted to determine the sensitivity of white sturgeon (Acipenser transmontanus) to the toxicological effects of elevated dietary selenium (Se). Juvenile white sturgeon were fed diets supplemented with Se in the form Of L-selenomethionine (SeMet), resulting in dietary concentrations of 0.4, 9.6, 20.5, 41.7, 89.8, and 191.1 mu g Se/g diet on a dry weight basis. Effects of dietary SeMet on survival, swimming activity, growth, whole-body proximate composition, tissue Se concentrations, and histopathology were determined. Sturgeon survival among treatment groups did not differ significantly with a mean survival rate of 99 +/- 0.43% across all groups. A significant decrease (p < 0.05) in swimming activity and growth rate was observed in sturgeon fed at or above 41.7 mu g Se/g diet. Dietary SeMet concentrations were negatively correlated with whole-body protein and lipid content, but positively correlated with ash and moisture content. Selenium accumulated. in the kidney, muscle, liver, gill, and plasma tissues in a dose-dependent manner. Histopathological alterations in the liver and kidney were observed in sturgeon fed above 20.5 mu g Se/g diet. The threshold dietary Se toxicity concentration for white sturgeon was estimated to lie between 10 and 20 jig Se/g diet based on the histopathological alterations in the kidney. Research examining the consequences of elevated dietary Se concentrations on more sensitive life stages and the interactive effects of Se with other chemical or physical stressors are needed in order to determine if dietary threshold should be lowered to minimize the potential impacts of Se on white sturgeon in the San Francisco Bay-Delta. (c) 2006 Elsevier B.V. All rights reserved.

An 8-week growth trial was conducted to determine the sensitivity of white sturgeon (Acipenser transmontanus) to the toxicological effects of elevated dietary selenium (Se). Juvenile white sturgeon were fed diets supplemented with Se in the form Of L-selenomethionine (SeMet), resulting in dietary concentrations of 0.4, 9.6, 20.5, 41.7, 89.8, and 191.1 mu g Se/g diet on a dry weight basis. Effects of dietary SeMet on survival, swimming activity, growth, whole-body proximate composition, tissue Se concentrations, and histopathology were determined. Sturgeon survival among treatment groups did not differ significantly with a mean survival rate of 99 +/- 0.43% across all groups. A significant decrease (p < 0.05) in swimming activity and growth rate was observed in sturgeon fed at or above 41.7 mu g Se/g diet. Dietary SeMet concentrations were negatively correlated with whole-body protein and lipid content, but positively correlated with ash and moisture content. Selenium accumulated. in the kidney, muscle, liver, gill, and plasma tissues in a dose-dependent manner. Histopathological alterations in the liver and kidney were observed in sturgeon fed above 20.5 mu g Se/g diet. The threshold dietary Se toxicity concentration for white sturgeon was estimated to lie between 10 and 20 jig Se/g diet based on the histopathological alterations in the kidney. Research examining the consequences of elevated dietary Se concentrations on more sensitive life stages and the interactive effects of Se with other chemical or physical stressors are needed in order to determine if dietary threshold should be lowered to minimize the potential impacts of Se on white sturgeon in the San Francisco Bay-Delta. (c) 2006 Elsevier B.V. All rights reserved.

An 8-week growth trial was conducted to study carbohydrate utilization by white sturgeon fed diets containing glucose or hydrolyzed potato starch (HPS). Four diets supplemented with 15% or 30% of glucose or HPS and a control diet with no added carbohydrate were each fed to triplicate groups of fish. The diets were processed by a 3-min 80 degrees C microwave moist heating, followed by 1-h 70 degrees C drying. Feeding rates varied from 1.7% to 3.2% body weight day(-1) so that all treatment groups were fed the same amount of dietary protein and lipid. The HPS groups showed the highest (P<0.05) specific growth rate, followed by the control, and then by the glucose groups. Feed efficiency was highest in the control and 15% HPS group followed by the 30% HPS group, and lowest in the glucose groups. Protein and energy retentions, whole body lipid, and muscle glycogen showed a similar pattern; with the glucose groups significantly lower than the control and HPS groups, whereas there was no difference among the control and HPS groups. A lower lysine and glucose in the glucose than control diets suggested that a severe Maillard reaction had occurred in the moist heat process, drying, and storage of the glucose diets. This is supported by the significantly lower plasma lysine concentrations in sturgeon fed the glucose diets than those fed the control diet. Sturgeon fed the glucose diets also showed significantly lower concentrations of plasma protein, cysteine, and hydroxyproline than those fed the control diet, whereas concentrations of liver glycogen and plasma alanine, gamma-aminobutyric acid and proline were significantly higher in sturgeon fed the glucose than the control and HPS diets. In conclusion, growth performances of sturgeon were not adversely affected by 15% HPS in the diet but severe Maillard reaction in the glucose diets resulted in significant reduction in the growth performances of the fish. (C) 2005 Elsevier B.V. All rights reserved.

An 8-week growth trial was conducted to study carbohydrate utilization by white sturgeon fed diets containing glucose or hydrolyzed potato starch (HPS). Four diets supplemented with 15% or 30% of glucose or HPS and a control diet with no added carbohydrate were each fed to triplicate groups of fish. The diets were processed by a 3-min 80 degrees C microwave moist heating, followed by 1-h 70 degrees C drying. Feeding rates varied from 1.7% to 3.2% body weight day(-1) so that all treatment groups were fed the same amount of dietary protein and lipid. The HPS groups showed the highest (P<0.05) specific growth rate, followed by the control, and then by the glucose groups. Feed efficiency was highest in the control and 15% HPS group followed by the 30% HPS group, and lowest in the glucose groups. Protein and energy retentions, whole body lipid, and muscle glycogen showed a similar pattern; with the glucose groups significantly lower than the control and HPS groups, whereas there was no difference among the control and HPS groups. A lower lysine and glucose in the glucose than control diets suggested that a severe Maillard reaction had occurred in the moist heat process, drying, and storage of the glucose diets. This is supported by the significantly lower plasma lysine concentrations in sturgeon fed the glucose diets than those fed the control diet. Sturgeon fed the glucose diets also showed significantly lower concentrations of plasma protein, cysteine, and hydroxyproline than those fed the control diet, whereas concentrations of liver glycogen and plasma alanine, gamma-aminobutyric acid and proline were significantly higher in sturgeon fed the glucose than the control and HPS diets. In conclusion, growth performances of sturgeon were not adversely affected by 15% HPS in the diet but severe Maillard reaction in the glucose diets resulted in significant reduction in the growth performances of the fish. (C) 2005 Elsevier B.V. All rights reserved.

Genetics professor Dr. Bernie May of the University of California at Davis and Sea Grant Trainee Dr. Jeff Rodzen were funded to develop a breeding program for broodstock at Stolt Sea Farm, the state’s largest producer of white sturgeon caviar. The goal of the project was twofold: to develop a breeding plan for slowing the rate of inbreeding of offspring and to investigate whether commercially desirable traits—superior growth rates, enhanced caviar yield and early sexual maturity—can be selectively bred.

Genetics professor Dr. Bernie May of the University of California at Davis and Sea Grant Trainee Dr. Jeff Rodzen were funded to develop a breeding program for broodstock at Stolt Sea Farm, the state’s largest producer of white sturgeon caviar. The goal of the project was twofold: to develop a breeding plan for slowing the rate of inbreeding of offspring and to investigate whether commercially desirable traits—superior growth rates, enhanced caviar yield and early sexual maturity—can be selectively bred.

The overall intent of this project was to develop a breeding plan for white sturgeon, using Stolt Sea Farm California LLC as a model system for broodstock management and selection using molecular markers. While the title of this project implies the function of the breeding plan to be of maintaining existing genetic variation as inferred from nuclear DNA markers, it is in the best interest of those parties involved in commercial production of this species to evaluate the feasibility of directed selection for economic traits such as growth rate. Thus, this project involves the estimation of quantitative genetic variation in addition to developing specific applications of molecular markers to broodstock management. Recommendations for their integration into a breeding plan and an overview of our research will be summarized in a manuscript being prepared (Rodzen et al. in prep4).

Nine tetramer [GATA]n microsatellite systems were developed for use in the white sturgeon, Acipenser transmontanus. We report inheritance patterns for these nine systems, which range from one possible disornic system to tetrasomy and octosomy, with some systems containing null alleles. Due to the complex modes of inheritance underlying these systems and the highly duplicated nature of the genome, we propose each allele be scored as its own dominant marker, similar to AFLPs or RAPDs. The utility of this method is validated by the observation that individual alleles within a microsatellite system generally fit the expectation for independent transmission and fit the expected transmission frequency for single copy nuclear markers.

The overall intent of this project was to develop a breeding plan for white sturgeon, using Stolt Sea Farm California LLC as a model system for broodstock management and selection using molecular markers. While the title of this project implies the function of the breeding plan to be of maintaining existing genetic variation as inferred from nuclear DNA markers, it is in the best interest of those parties involved in commercial production of this species to evaluate the feasibility of directed selection for economic traits such as growth rate. Thus, this project involves the estimation of quantitative genetic variation in addition to developing specific applications of molecular markers to broodstock management. Recommendations for their integration into a breeding plan and an overview of our research will be summarized in a manuscript being prepared (Rodzen et al. in prep4).

Nine tetramer [GATA]n microsatellite systems were developed for use in the white sturgeon, Acipenser transmontanus. We report inheritance patterns for these nine systems, which range from one possible disornic system to tetrasomy and octosomy, with some systems containing null alleles. Due to the complex modes of inheritance underlying these systems and the highly duplicated nature of the genome, we propose each allele be scored as its own dominant marker, similar to AFLPs or RAPDs. The utility of this method is validated by the observation that individual alleles within a microsatellite system generally fit the expectation for independent transmission and fit the expected transmission frequency for single copy nuclear markers.

Significant progress has been achieved during the past several years in understanding endocrine control of reproduction in white sturgeon, Acipenser transmontanus (Moberg et al., 1995; Doroshov et al., 1997), however the regulation of prespawning oocyte development and the effects of environmental factors on this phase have been inadequately studied. Field and experimental observations suggest that the thermal regime of rivers plays a pivotal role in environmental control of tinal ovarian maturation (FOM) and spawning of wild sturgeon (Dettlaff et al., 1993), and constant, elevated temperatures have been found to result in decreased plasma sex steroid concentrations, a high incidence of ovarian atresia, and spawning failure in cultured sturgeon (Webb et al., 1999). Chapter l reviews our current knowledge of sturgeon reproductive endocrinology and the effects of environmental factors, specifically temperature, on the late phase of oogenesis.The effects of environmental temperature, ultimately mediated y brain-pituitary secretions, can be tested at the level of the ovary by observations on sex steroid secretion correlated with oocyte development. The objectives of this project were l) to determine baseline steroidogenic profiles in prespawning female sturgeon exposed to seasonal temperature, 2) to identify native steroid hormones involved in oocyte maturation, and 3) to examine and compare ovarian development, acquisition of maturational competence, and plasma sex steroid profiles in gravid females reared in warm water and transferred to cold water in the late fall or early spring.Chapter 2 characterizes the baseline plasma steroid profile and in vitro ovarian steroid secretion in two females held at seasonal temperatures throughout FOM and ovulation. Ovarian follicles were incubated with or without pregnenolone (P5), and concentrations of testosterone (T), 11-ketotestosterone (KT), estradiol (E2), and 17a, 208-dihydroxy-4-pregnen-3-one (17, 208-P) were measured by ra

Significant progress has been achieved during the past several years in understanding endocrine control of reproduction in white sturgeon, Acipenser transmontanus (Moberg et al., 1995; Doroshov et al., 1997), however the regulation of prespawning oocyte development and the effects of environmental factors on this phase have been inadequately studied. Field and experimental observations suggest that the thermal regime of rivers plays a pivotal role in environmental control of tinal ovarian maturation (FOM) and spawning of wild sturgeon (Dettlaff et al., 1993), and constant, elevated temperatures have been found to result in decreased plasma sex steroid concentrations, a high incidence of ovarian atresia, and spawning failure in cultured sturgeon (Webb et al., 1999). Chapter l reviews our current knowledge of sturgeon reproductive endocrinology and the effects of environmental factors, specifically temperature, on the late phase of oogenesis.The effects of environmental temperature, ultimately mediated y brain-pituitary secretions, can be tested at the level of the ovary by observations on sex steroid secretion correlated with oocyte development. The objectives of this project were l) to determine baseline steroidogenic profiles in prespawning female sturgeon exposed to seasonal temperature, 2) to identify native steroid hormones involved in oocyte maturation, and 3) to examine and compare ovarian development, acquisition of maturational competence, and plasma sex steroid profiles in gravid females reared in warm water and transferred to cold water in the late fall or early spring.Chapter 2 characterizes the baseline plasma steroid profile and in vitro ovarian steroid secretion in two females held at seasonal temperatures throughout FOM and ovulation. Ovarian follicles were incubated with or without pregnenolone (P5), and concentrations of testosterone (T), 11-ketotestosterone (KT), estradiol (E2), and 17a, 208-dihydroxy-4-pregnen-3-one (17, 208-P) were measured by ra

The overall aim of this project was to understand the mode of sex determination mechanism operates in chondrostean species. The following hypotheses were tested: i) white sturgeon has a genetic sex determination system, ii) one of the sexes in sturgeon is heterogametic, and iii) sex-specific DNA polymorphisms exist between the sexes.Several experimental approaches derived from the fields of transmission, molecular, and cytogenetics were used to examine the nature of the sex determination process.In the first series of experiments (Chapter 2) ploidy manipulation techniques were used to produce gynogenetic and polyploid white sturgeon. A novel random amplified polymorphic DNA (RAPD)-based technique was developed to rapidly assess the overall success of treatments designed to induce gynogenesis, and measuring erythrocyte nuclei size with a Coulter Counter was found to be a rapid and accurate technique for ploidy analysis in sturgeon. Both sexes were observed in 23-24 month old gynogenetic progeny groups derived from four different females supporting the hypothesis that white sturgeon has a female heterogametic (ZW:ZZ) genetic sex determination system. The proportion of males in diploid (48%), gynogenetic (18%), and triploid (14%) progeny groups derived from the same female suggested that the sex-determining element on the W chromosome segregates independently of the centromere. In the second series of experiments (Chapter 3) various molecular techniques were used in an attempt to isolate genetic markers for the identification of sex in white sturgeon. Subtractive hybridization, representational difference analysis and bulked segregant analysis were used, in conjunction with genetically unique groups of sturgeon, which were specifically developed to increase the probability of isolating sex-specific DNA sequences. DNA sequences associated with sex in white sturgeon were not identified. These results suggest that either 1) there are no sex-specific sequences in sturgeo

The overall aim of this project was to understand the mode of sex determination mechanism operates in chondrostean species. The following hypotheses were tested: i) white sturgeon has a genetic sex determination system, ii) one of the sexes in sturgeon is heterogametic, and iii) sex-specific DNA polymorphisms exist between the sexes.Several experimental approaches derived from the fields of transmission, molecular, and cytogenetics were used to examine the nature of the sex determination process.In the first series of experiments (Chapter 2) ploidy manipulation techniques were used to produce gynogenetic and polyploid white sturgeon. A novel random amplified polymorphic DNA (RAPD)-based technique was developed to rapidly assess the overall success of treatments designed to induce gynogenesis, and measuring erythrocyte nuclei size with a Coulter Counter was found to be a rapid and accurate technique for ploidy analysis in sturgeon. Both sexes were observed in 23-24 month old gynogenetic progeny groups derived from four different females supporting the hypothesis that white sturgeon has a female heterogametic (ZW:ZZ) genetic sex determination system. The proportion of males in diploid (48%), gynogenetic (18%), and triploid (14%) progeny groups derived from the same female suggested that the sex-determining element on the W chromosome segregates independently of the centromere. In the second series of experiments (Chapter 3) various molecular techniques were used in an attempt to isolate genetic markers for the identification of sex in white sturgeon. Subtractive hybridization, representational difference analysis and bulked segregant analysis were used, in conjunction with genetically unique groups of sturgeon, which were specifically developed to increase the probability of isolating sex-specific DNA sequences. DNA sequences associated with sex in white sturgeon were not identified. These results suggest that either 1) there are no sex-specific sequences in sturgeo

To better understand the concept of biocultural diversity and its value in species conservation, my research explored the role of local fishers’ knowledge and cultural values in decision-making about the conservation of threatened, culturally significant fish in the Lower Fraser River (Canada) and the Mekong River (Thailand). This thesis uses exploratory, qualitative research into the case of the White Sturgeon or “skō:wech” (Acipenser transmountanus), and the Mekong Giant Catfish or “Plaa buek” (Pangasius gigas). Through semi-structured interviews and a review of existing information, this research set out to determine: 1) What kinds of knowledge do local fishers have about threatened species? 2) Are Local and Traditional Ecological Knowledge influencing processes (research, assessment, monitoring) and informing conservation strategies for threatened species? If so, how? 3) Do cultural values influence conservation strategies for threatened species? If so, how? 4) Are there any opportunities to increase the role of local knowledge and cultural values to enhance existing conservation strategies and achieve both biological and cultural diversity conservation? Results suggest although there are some examples of success, there are opportunities to increase the influence local fishers’ knowledge and values have in current approaches employed to conserve species with special conservation status. Maintaining some level of traditional fishery, and support for cultural practices, education and outreach are critical aspects of maintaining culture, values and knowledge systems linked to these threatened species.