Orientador: Otto Bismarck Fazzano Gadig / Resumo: A raia elétrica cega Benthobatis kreffti é endêmica do Altântico Sul Ociedental e apresenta distribuição restrita desde o sul até o sudeste Brasileiros, ocorrendo em profundidades entre 400 e 600 m. Apesar de seu extremo endemismo, sua biologia é virtualmente desconhecida, especialmente no que diz respeito à porção norte de sua distribuição. O objetivo deste trabalho foi estudar a estrutura populacional e biologia reprodutiva desta espécie, no talude continental do estado de São Paulo. Os indivíduos foram capturados em julho e agosto de 2003 e dezembro de 2007 no cruzeiro científico Soloncy Moura, o qual operou em 492-501 m de profundidade entre os municípios de Santos e Cananéia. Quanto à composição de captura, B. kreffti foi o condricte mais capturado, seguido por Gurgesiella dorsalifera. Os demais foram Hydrolagus matallanasi, Dipturus sp. e Torpedo, sp. Quanto à estrutura em tamanho, fêmeas diferem de machos por apresentarem maiores comprimentos (máximo de 299 mm em fêmeas e 256 mm em machos). A razão sexual total foi diferente de 1:1, bem como para indivíduos adultos. Nos outros estágios de maturidade considerados (imaturo e em desenvolvimento), não houve diferença significativa. A relação comprimento-peso e o tamanho onde 50% da população encontra-se maduro (LT50) também foram diferentes entre os sexos, em favor das fêmeas. Fêmeas apresentaram LT50 de 191 mm enquanto machos maturam em 176 mm. A fecundidade uterina foi de três embriões por fêmea, com embriões nascendo en... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The blind electric ray Benthobatis kreffti is endemic to the South West Atlantic and has a restricted distribution, from south and southeast Brazil, occurring in 400-600 m depth. Despite its endemism, its biology is virtually unknown, especially concerning the north extreme of its distribution. For this reason, the aim of this work was to study the population structure and reproductive biology of B. kreffti off São Paulo State continental slope. Individuals were captured in July and August of 2003 and December 2007 during the scientific cruise Soloncy Moura, operating in 492-501 m depth between Santos and Cananéia municipalities. Benthobatis kreffti was the most captured chondrichthyan, followed by Gurgesiella dorsalifera. Other chondrichthyan captured were: Hydrolagus matallanasi, Dipturus sp and Torpedo sp.. Concerning size structure, females were larger than males (females: 299 mm; males: 256 mm total length). Total sex ratio was different from 1:1, as well as for adult individuals. At other maturity stages considered (immature and developing), no differences were observed. The length-weight relationship and size at 50 % maturity (LT50) were also different between sexes, biased toward females. Female´s LT50 was 191 mm, while in males, LT50 was 176 mm total length. Uterine fecundity was three embryos/ female, with size at birth estimated in 90-100 mm total length (about1/3 of the total length recorded for this species). / Mestre

Fischgemeinschaften in Seen sind zunehmenden Umweltveränderungen unterworfen. Die Analyse des Einflusses abiotischer und biotischer Faktoren auf die Größenstruktur von Fischgemeinschaften ist entscheidend, um die Entwicklung von Seeökosystemen im Zuge von Umweltveränderungen vorhersagen zu können. Es ist jedoch schwierig Fische in Seen zu beproben, da Fanggeräte selektiv sind. Die Qualität und Vergleichbarkeit von Fischfängen durch Angler, Kiemennetze, Schleppnetze und Hydroakustik wurden untersucht. Anglerfänge eignen sich begrenzt für vergleichende Fischbestandsuntersuchungen. Vertikale Hydroakustik eignet sich für die Fischbiomassequantifizierung in geschichteten Seen. Der Beprobungsaufwand von Kiemennetzen kann reduziert werden, wenn zeitnah hydroakustische Untersuchungen statt finden. Schleppnetze eignen sich für die Beprobung von pelagischen Fischen in tiefen Seen. Die Größenstruktur von Fischgemeinschaften unterschied sich auf regionaler und überregionaler Ebene entlang abiotischer und biotischer Gradienten. Die regionale Studie zeigte, dass tiefe nährstoffarme Seen mit hohen Raubfischabundanzen durch mehr große Fische gekennzeichnet waren. Nährstoffreiche Flachseen mit wenigen Raubfischen zeigten höhere Anteile von mittleren Fischgrößen. Im überregionalen Vergleich führten Temperaturpräferenzen der Fischarten zu zwei Fischgemeinschaften, die sich in ihrer Größenzusammensetzung unterschieden. Ein hoher Anteil großer Salmoniden war typisch für hochgelegene Kaltwasserseen im Norden und Süden Europas. Flachlandseen mit Kühl- und Warmwasserfischen zeichneten sich durch eine Dominanz von kleinen Fischen aus. Das lässt vermuten, dass Fischgemeinschaften in Flachlandseen relativ robust gegenüber Umweltveränderungen reagieren. Kaltwasserfischgemeinschaften könnten im Zuge der Klimaerwärmung starken Änderungen unterliegen, da eine Veränderung in der Artenzusammensetzung von einer Verschiebung in der Größenstruktur hin zu mehr kleinen Fischen begleitet sein wird. / Lake fish assemblages are increasingly exposed to environmental change in their habitats. The investigation of abiotic and biotic factors and their effects on the size structure of lake fish is essential for predicting the response of fish assemblages to environmental change. However, sampling of lake fish is challenging because sampling gears are selective. The quality and correspondence of fish catches from angling, gillnetting, trawling and hydroacoustics were analysed. Non-standardised catch data from recreational angling were of limited quality for a comparison of fish stocks. Vertical hydroacoustics is an efficient method to quantify fish biomass in stratified lakes. Sampling effort of multi-mesh gillnets can be reduced when fish abundance estimates are derived from contemporarily operating hydroacoustics. Trawling is useful to sample pelagic fish assemblages in deep lakes. The size structures of fish assemblages differed on a small and a large geographical scale along gradients of abiotic and biotic lake descriptors and differences in fish assemblage composition. At a small geographical scale assemblages in deep and less nutrient-rich lakes with high predator abundances were characterised by a higher proportion of large fish. Shallow nutrient-rich lakes with few predators were characterised by more medium-sized fish. At a large geographical scale thermal optima of fish generated two types of assemblages with different size structures. A high proportion of large salmonids was observed in coldwater lakes at high elevation sites in northern and southern Europe. Lowland lakes with cool- and warmwater fish were dominated by small-sized individuals. The results suggest that lowland lake fish assemblages are relatively robust against environmental change. Coldwater fish assemblages instead may suffer dramatic consequences from global warming as expected species shifts are likely to be accompanied by shifts in the size structure towards smaller individuals.