504 resultados para ICTIOFAUNA DEMERSAL
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Este estudo foi desenvolvido no riacho Taquaral, que integra a Bacia hidrográfica do Pirapitingui, localizado na cidade de Itu, estado de São Paulo. A pesquisa foi conduzida com a finalidade de comparar a diversidade da ictiofauna em três pontos distintos de um trecho do riacho, além de obter variáveis ambientais físicas e químicas que poderiam distinguir as características abióticas e influenciar as particularidades bióticas de cada ponto. As coletas foram realizadas com materiais de pesca que consistiram em redes de espera, peneira e armadilhas de fundo do tipo covo. Uma lista das espécies foi elaborada utilizando-se de cálculo de riqueza, abundância relativa e abundância total por ambiente amostrado para então realizar as análises de diversidade se utilizando do Índice de Shannon por local de coleta, o qual assume que os indivíduos são amostrados ao acaso com origem em uma população indefinidamente grande e que todas as espécies são representadas na amostra. Além desse índice foram considerados os índices de similaridade de Jaccard, que compara a similaridade das espécies de dois locais levando em conta a presença ou ausência das espécies e o Índice de Morisita -Horn que abrange também a abundância dessas espécies. No total foram capturados 3490 exemplares pertencentes a 5 ordens e 7 famílias, em um total de 15 espécies, sendo que em um dos pontos (ponto1) foi observado menor quantidade de espécies e menor número de exemplares (8 espécies e 49 exemplares). Os demais pontos (pontos 2 e 3) obtiveram igual número de espécies (13), além dos maiores números em exemplares ( 1447 e 1994, respectivamente). Os resultados apontam a existência de diferenças nas características ambientais, também resultantes de influências antrópicas na região e consequente diferenciação na diversidade dos três pontos amostrados. A diversidade observada no Ponto 1, a partir do Índice de Shannon, foi a maior em...
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Programa de doctorado: Medio Ambiente y Gestión de Recursos Marinos. La fecha de publicación es la fecha de lectura
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An appropriate management of fisheries resources can only be achieved with the continuous supply of information on the structure and biology of populations, in order to predict the temporal fluctuations. This study supports the importance of investigating the bio-ecology of increasingly exploited and poorly known species, such as gurnards (Osteichthyes, Triglidae) from Adriatic Sea (Mediterranean), to quantify their ecological role into marine community. It also focuses on investigate inter and intra-specific structuring factor of Adriatic population. These objectives were achieved by: 1) investigating aspects of the population dynamics; 2) studying the feeding biology through the examination of stomach contents; 3) using sagittal otoliths as potential marker of species life cycle; 4) getting preliminary data on mDNA phylogeny. Gurnards showed a specie-specific “critical size” coinciding with the start of sexual maturity, the tendency to migrate to greater depths, a change of diet from crustaceans to fish and an increase of variety of food items eaten. Distribution of prey items, predator size range and depth distribution were the main dimensions that influence the breadth of trophic niche and the relative difference amongst Adriatic gurnards. Several feeding preferences were individuated and a possible impact among bigger-size gurnards and other commercial fishes (anchovy, gadoids) and Crustacea (such as mantis prawn and shrimps) were to be necessary considered. Otolith studies showed that gurnard species have a very fast growth despite other results in other areas; intra-specific differences and the increase in the variability of otolith shape, sulcus acusticus shape, S:O ratios, sulcus acusticus external crystals arrangement were shown between juveniles and adults and were linked to growth (individual genetic factors) and to environmental conditions (e.g. depth and trophic niche distribution). In order to facilitate correct biological interpretation of data, molecular data were obtained for comparing morphological distance to genetic ones.
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In this study we provide a baseline data on semidemersal fish assemblages and biology in a heterogeneous and yet less studied portion of the shelf of Antalya Gulf. The distribution of fish abundance in three transects subjected to different fisheries regulations (fishery vs non fishery areas), and including depths of 10, 25, 75, 125, 200 m, was studied between May 2014 and February 2015 in representative months of winter, spring, summer and autumn seasons. A total of 76 fish species belonging to 40 families was collected and semidemersal species distribution was analyzed in comparison with the whole community. Spatial distribution of fish was driven mainly by depth and two main assemblages were observed: shallow waters (10-25; 75 m) and deep waters (125-200 m). Significant differences among transects were found for the whole community but not for the semidemersal species. Analysis showed that this was due to a strong relation of these species with local environmental characteristics rather than to a different fishing pressure over transects. Firstly all species distribute according to the bathymetrical gradient and secondly to the bottom type structure. Semidemersal species were then found more related to zooplankton and suspended matter availability. The main morphological characteristics, sex and size distribution of the target semidemersal species Spicara smaris (Linnaeus, 1758), Saurida undosquamis (Richardson, 1848), Pagellus acarne (Risso, 1827) were also investigated.