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Prerequisites for the remediation of the indigenous sturgeons Acipenser sturio Linnaeus 1758 and A. oxyrinchus Mitchill 1815 in river systems of northern Germany - development of methods and contributions towards scientific criteria and concepts for a recovery management plan

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Prerequisites for the remediation of the indigenous sturgeons Acipenser sturio Linnaeus 1758 and A. oxyrinchus Mitchill 1815 in river systems of northern Germany - development of methods and contributions towards scientific criteria and concepts for a recovery management plan

Jörn Geßner (Unbekannter Einband, Englisch)

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Beschreibung

Sturgeons have become increasingly threatened world-wide by commercial exploitation and environmental stress. Historically ranging from the Black Sea via the Mediterranean and the Eastern North Atlantic to the North, Baltic and White Sea (Holčik et al., 1989) Acipenser sturio (Linnaeus, 1758) dramatically declined during the 19th and particularly the 20th century. Today it is considered missing or extinct in German waters. Only in the Gironde (France) a remnant population persists in decreasing numbers. It was evaluated that a combination of overfishing, hydroconstruction, degradation of water quality, and destruction of spawning habitat were the main reasons for the decline. The work presented contributed to the development of an Action Plan for the protection and recovery of A. sturio under the Bern Convention, resulting in national plans. Associated management plans identify protection measures and their control. Prerequisites were developed, being summarized in part in this thesis. Morphological and phylogenetic as well as population genetic analyses of recent and historic material have proven the existence of two different species, the American Atlantic sturgeon (A. oxyrinchus) in the Baltic Sea and the European Atlantic sturgeon (A. sturio) in the North Sea leading to a separation of the remediation activities, thereby requiring broodstock development for both species. Utilizing similar strategies, the broodstock is developed from F1 fish based upon a transfer of French fish in 1996 in A. sturio as an ex-situ measure while F1 and and adult fish from commercial fisheries are used in A. oxyrinchus. Therefore, intercontinental live transport techniques were tested in a pressure chamber simulated flight experiment. Water quality, respiration frequencies, blood gas pressure, blood ion contents, Cortisol and other parameters were monitored over 366h following exposition. At air transport these parameters were used to assess recovery of the fish following transport and for optimization. The physiological and behavioural responses of early life stages towards sand and gravel substrate were verified for 15 days upon hatch in A. oxyrinchus. Substrate utilization of the free embryos differed significantly during the first 5 days upon hatch; resulting in significant differences in growth and energy contents. The onset of exogenous feeding in the control and sand groups was accellerated compared to the gravel group. The energy content at onset of exogenous feeding in the gravel group exceeded that in the other groups by 14%. Cortisol between the 3 groups did not differ significantly due to high standard deviation. In accordance with in situ data the results strongly suggest that gravel is beneficial for the development of the free embryos of A. oxyrinchus not only reducing predation but also impacting the physiological performance. The results were transferred in a habitat assessment for reproduction sites as a key element for population integrity. Fourteen historic spawning sites were surveyed comprising the rivers Odra, Warta, Prosna, Notec and Drawa. Only two sites revealed suitable substrates but high nutrient loads impaired suitability, only one site was considered fully functional. Over the last two decades the increasing catches of exotic sturgeon species have been monitored based on a reward system in commercial fisheries. A total of 227 records were reported until 2000 and more than 550 to date. Major introductions resulted from escapements from fish farms as well as from deliberate releases by anglers. The study revealed significant changes in species composition reflecting species composition in sturgeon aquaculture. The exotic specimens thrive under natural conditions; potentially affecting restoration efforts by concurrence, transferring diseases or potentially hybridization. The data set also was used to evaluate by-catch of sturgeons by fishing methods. In commercial fisheries, gill-nets contributed 37% to the total catch. Gear modifications were tested during 11 fishing trials in ponds using A. baerii as a model to reduce by-catch of sturgeons and the selectivity for target species in Szczecin Lagoon. A 97% reduction in sturgeon by catch but also significantly decreased CPUE of Eurasian perch were the main results compared to standard nets. The results helped to adopt strategies for the remediation activities. Weniger zeigen

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Produktinformationen

Technische Daten

Erscheinungsdatum

01.07.2009

Sprache

Englisch

EAN

9783866244481

Herausgeber

Winter Industries

Serien- oder Bandtitel

Dissertation Premium

Sonderedition

Nein

Autor

Jörn Geßner

Seitenanzahl

216

Auflage

Einbandart

Unbekannter Einband

Bandzählung

1548

Schlagwörter

remediation, oxyrinchus, management, Acipenser, protection, sturgeon, sturio

Höhe

210 mm

Breite

15 cm

Warnhinweise und Sicherheitsinformationen

Informationen nach EU Data Act

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