L'esturgeon européen Acipenser sturio (Linnaeus, 1758) était un poisson commun de nos fleuves jusqu'au début du 20e siècle. Toutes ses populations sont maintenant éteintes sauf une qui survit dans le bassin Gironde-Garonne-Dordogne en France. Les données disponibles sur l'espèce restent très partielles car elles proviennent quasi exclusivement de cette population relictuelle. Au cours de cette thèse, plus d'une centaine d'échantillons anciens d'esturgeons restes archéologiques ou spécimens naturalisés conservés dans les muséums d'histoire naturelle ont été analysé grâce aux méthodes de la paléogénétique. Ces analyses génétiques ont été réalisées sur l'ADN mitochondrial (surtout la Dloop) ainsi que sur cinq loci microsatellites qu'il a été nécessaire d'adapter aux méthodes d'étude de l'ADN ancien. Les données paléogénétiques obtenues ont permis d'étudier : 1) les relations de l'esturgeon européen avec les autres espèces d'esturgeons vivant ou ayant vécu en Europe, en particulier l'esturgeon de l'Adriatique A. naccarii et l'esturgeon atlantique A. oxyrinchus. 2) la diversité génétique de l'esturgeon européen sur l'ensemble de son ancienne aire de répartition. 3) la diversité génétique d'une population d'esturgeon européen au cours du temps la population du Rhône, d'une période où elle était florissante jusqu'à son extinction. L'ensemble de ces données ont été discuté à la lumière de la conservation de l'espèce, qui est aujourd'hui en danger critique d'extinction. / The European sturgeon Acipenser sturio (Linnaeus, 1758) was a common fish of our rivers until the beginning of the 20th century. All populations are now extinct except one which survives in the Gironde-Garonne-Dordogne basin in France. Data available on this species are only partial because they only stem from this relictual population. During this thesis, more than one hundred ancient sturgeon samples archaeological remains or naturalized museum specimens were analysed by paleogenetics means. These genetics anlyses were carried out on mitochondrial DNA (mainly the Dloop) and five microsatellites loci which were adapted to ancient DNA methodologies. Paleogenetics data that we obtained were used to study : 1) A. sturio interactions with other sturgeon species which live or lived in Europe, especially the Adriatic sturgeon A. naccarii and the atlantic sturgeon A. oxyrinchus. 2) the genetic diversity of A. sturio all over its former geographical range. 3) genetic diversity of a population of the European sturgeon through time the Rhone River population from a period it was flourishing until its extinction. All these data were considered in the light of the species conservation, since A. sturio is now critically endangered.

The tidal James River, a focus of VCU's Atlantic Sturgeon program, supports both commercial shipping and hydraulic dredging. These anthropogenic threats present documented but preventable sources of mortality to the endangered species. Using three separate VEMCO Positioning System (VPS) receiver arrays, spatial data of previously-tagged fish were collected. ArcGIS and Programita software were used to analyze fish spatial distributions in the presence and absence of potential threats, using additional data including automatic identification system (AIS) vessel locations, vessel passages compiled using camera footage, and dredge records provided by the US Army Corps of Engineers. The data showed a change in distribution associated with vessels that varied according to river width but not vessel type. Dredging was associated with differences in spatial distribution, but more clearly for adults than sub-adults. The responses of Atlantic Sturgeon provide information necessary to propose potential threat mitigations, including seasonal restrictions for both vessels and dredging.

With the global rise in frequency of harmful algal blooms in estuarine environments comes an increase in prevalence of toxic metabolites, such as microcystin (MC), that some of the cyanobacteria involved will produce. At high concentrations, MC may accumulate in consumer tissues and have deleterious effects on organisms; however impacts of the toxin on aquatic living resources at ecologically relevant concentrations have not been widely documented. We analyzed the effects of MC on juveniles of five fish species from the James River, Virginia to determine if MC has the potential to impede growth. Using three separate experimental approaches, it was shown that exposure to concentrations of the toxin currently observed in the James River estuary do not appear to significantly impact the growth or survivorship of tested fish species. Extraneous factors in parts of the study led to an inability to draw clear conclusions on mortality or growth impacts; however it is evident from the experiments that at least some of the fish species have biological mechanisms in place that allow them to effectively eliminate the toxin from their systems. An ability to extricate the toxin suggests the possibility for fishes to withstand MC exposures and sustain few negative health impacts at low MC concentrations.

Namao virus (NV) was associated with mortality in lake sturgeon Acipenser fulvescens reared as part of a conservation stocking program for this endangered species in Manitoba, Canada. The virus itself was large, doubly encapsidated and icosahedral-shaped. Phylogenetic analyses using the major capsid protein showed that NV and other epitheliotropic sturgeon nucleo-cytoplasmic large DNA viruses shared a common evolutionary past and formed a distinct evolutionary lineage within Megavirales. Three PCR tests were developed and their analytical performance was validated for detection of these viruses. Testing of wild sturgeon revealed that NV is endemic in the Nelson River water basin in Manitoba. Bath exposure resulted in transmission of NV to healthy sturgeon. The gills appeared to be the initial site of infection with virus persisting in the head skin tissue for up to 62 days. The molecular tests will be useful tools for disease management in sturgeon conservation stocking programs. / October 2015

Die Studie enthält zwei Berichte. Rümmler, Heidrich und Pfeifer berichten über die kombinierte Satzkarpfen-Edelfischaufzucht in geschlossenen Kreislaufanlagen. Im zweiten Bericht referieren die Autoren Heidrich, Wedekind und Pfeifer über Optimierung biologischer und technologischer Parameter für die Aufzucht von Stören in geschlossenen Kreislaufanlagen.

In Sachsen gewinnt die Aufzucht von Stören in Teichen zunehmend an Bedeutung, insbesondere um die Wirtschaftlichkeit der Warmwasserteichwirtschaft zu verbessern. Mit der Störerzeugung wurden Kapazitäten für die Herstellung von Farmkaviar geschaffen. Dieser ist jedoch starken Qualitätsunterschieden unterworfen. Störe neigen zu einer starken Verfettung des Eingeweidekomplexes, des Filets und der Gonaden, was geschmackliche Probleme zur Folge hat. Es wurde untersucht, ob spezielle Futtermittel, die für die finale Aufzuchtphase von Stören angeboten werden, geeignet sind, die Kaviarqualität zu verbessern und der Verfettung entgegenzuwirken. Mit allen vier geprüften Futtermitteln konnten gute Zuwachsleistungen und eine Verbesserung der Produktqualität erreicht werden. Alle Futtermittel erwiesen sich als geeignet für die Störaufzucht in der finalen Aufzuchtsaison vor der Kaviargewinnung. Die eingesetzten Futtermittel hatten jedoch weder Einfluss auf die zu gewinnende Menge, noch auf die Qualität des Kaviars.

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.

No description available.

Rehabilitation of sturgeon populations requires an understanding of sturgeon autecology during all life stages, especially during early life when high mortality occurs. To begin to understand sturgeon early-life history I determined river of origin on a multi-basin scale (i.e., potential rivers of origin). I then determined habitat needs and early life demographics on a more localized scale (i.e., specific river). Trace elements differ between river reaches of the central US and may be used to determine origin of age-0 sturgeon. My trace element analyses suggested that age-0 sturgeon captured in the Middle Mississippi River, which extends from the confluence of the Missouri River downstream to the confluence of the Ohio River, drifted from as far upstream as the Gavins Point Dam on the Missouri River (> 1200 km), while other individuals originated locally in the Middle Mississippi River. On a more refined scale of habitats, I used trawling to identify habitat features used. Age-0 Scaphirhynchus sturgeon catch rates were highest around artificial structures (i.e., wing dikes) and island areas while main channel habitat comprised the lowest catch rates. Within these habitats, young sturgeon frequently occupied low velocities (i.e., ~0.1), moderate depths (i.e., 2 to 5 m), and sand substrate. Although determination of river of origin and specific habitats used are imperative for restoration, sturgeon populations are likely regulated by factors within habitats that affect early-life dynamics. Mean sturgeon growth rates ranged from 1.42-1.50 mm/d over the four years but did not differ among years. Individuals hatched over a 25 to 50-d period and peak hatch dates were between 10- 20 May during all years. Hatching coincided with optimum spawning temperatures of 17-20oC and a rise in river stage. Abundance was positively related to river stage, with longer durations of high water related increasing abundance. Mortality of age-0 sturgeon increased with the number of days where water temperature exceeded 28 oC. In the end this study has set benchmarks for understanding factors affecting the early-life ecology of Scaphirhynchus sturgeon.

Sturgeons (Chondrostei: Acipenseriformes) display markedly disjunct distributions with a wide occurrence in the northern hemisphere. Their unique benthic specializations, conserved morphology, evolutionary age, the variation in their basic diadromous life history, and the large public interest due to their near extinction or critically endangered status make sturgeons and paddlefishes one of the most interesting group of vertebrates. In addition to that, ploidy diversity of Acipenseriformes possessing three ploidy groups having ~ 120 chromosomes, ~ 240 ? 270 chromosomes and ~ 360 chromosomes provides unique model for investigation of evolutionary processes which were going through the genome duplication events. Sturgeons are also notoriously known for their strong propensity to interspecific and intergeneric hybridization which can result in hybrids with various ploidy levels. All these facts make sturgeon genetics and cytogenetics a thriving but also complicated area for research. In the present work, the role of genome duplication and functional reduction evens in evolution of sturgeon species as well as sturgeons? ploidy levels and ploidy relationships among Acipenseriformes were investigated using molecular markers. In addition to that, clarification of origin of abnormal ploidy levels and observation of segregation pattern of microsatellite alleles in the course of hybridization of polyploid sturgeon species were included into this study. With regard to the all considerations and observations provided by this study we concluded that evolution of sturgeon species is still widely dynamic and ongoing process which might goes through the allopolyplodization as well as autopolyplidization events.