2013-08-192013-08-191999-11-23TORRES, Marcelo Ferreira. Variação sazonal e espacial da estrutura de comunidades dos peixes demersais da Região de Foz dos Rios Amazonas e Tocantins - PA (0º 10'S - 2º30'N; 47º50'W - 50º30'W) - Brasil. 1999. 75 f. Dissertação (Mestrado) - Universidade Federal do Pará, Museu Paraense Emílio Goeldi, Belém, 1999. Curso de Pós-Graduação em Zoologia.https://repositorio.ufpa.br/handle/2011/4144The composition, abundance and frequency of the demersal fish fauna from the Amazon estuary were studied in three areas which ones were defined as circumscribed within the isobath ranges of 5-10 m, 10-20 m and 20-50 m. The main objectives of this work were to compare the diversity, abundance and distribution of demersal fish fauna in these three areas during one hydrological cycle, and evaluate the infiuence of environmental variables on the community structure. Samples were taken on board of two piramutaba fishing vessels, using a bottom trawl net, for a given seasonal survey of six 15-day trips in the dry season (March and Apri1/97) and in the rainy season (August and September/97). A number of 91 species were caught in a total of 237 samples and Sciaenidae and Ariidae were the most diverse families, represented by 25% of total species. The Ariidae' species which ocurred in the area were very abundant. The most abundant species were Macrodon ancylodon (Sciaenidae) (56,2%) and Brachyplatystoma vaillantii (Pimelodidae) (13,6%) in the rainy season, and Macrodon ancylodon (31%) and Stellifer rastrifer (15,8%) (Sciaenidae) in the dry season. In area 1 Brachyplatystoma vaillantli (Pimelodidae) and Macrodon ancylodon (Sciaenidae) were the most abundant species in both periods, and the same occurred for Macrodon ancylodon and Stellifèr rastrifer (Sciaenidae) in area 2, and for Macrodon ancylodon (Sciaenidae) and Bagre bagre (Ariidae) in area 3. The most frequent species sampled were Macrodon ancylodon (Sciaenidae) (40,9%) and Anchoa spinifer (Engraulididae) (35%) in the rainy season, and Macrodon ancylodon (Sciaenidae) (45,6%) and Anus grandicassis (Ariidae) (38,4%) in the dry season. In area 1 Brachyplatystoma vaillantii and Brachyplatystoma flavicans (Pimelodidae) were the most frequent species, considering each period; the same was observed for Macrodon ancylodon (Sciaenidae) and Bagre bagre (Ariidae) in area 2, and Macrodon ancylodon (Sciaenidae) and Anchoa spinifér (Engraulididae), in area 3. The dominant species were: Macrodon ancylodon (Sciaenidae) in the rainy season (56% of the specimens collected); and Macrodon ancylodon, Stellifér rastrifer (Sciaenidae) and Anus quadriscutis (Ariidae) in dry season, which represented 61% of fishes caught. In area 1, Brachypiatystoma vaillantii (Pimelodidae) and Macrodon ancylodon (Sciaenidae), were dominant (73%) in the rainy season, and both of them together with Anus grandicassis (Ariidae) were dominant (53%) in the dry season. area 2 only Adacrodon ancylodon (Sciaenidae) was dominant (64%) in the rainy season, and Macrodon ancylodon and Stellifer rastrifèr (Sciaenidae) were dominant (53%) in the dry season. In area 3, just one species Macrodon ancylodon (Sciaenidae) was considered dominant (70% in the rainy season and 49% in the dry season). Distribution patterns were influenced by salinity. Area 1 presented the greatest diversity and evenness as compared with the others. Area 2 presented the greatest richness, and area 3 presented the highest dominance. Three communities were identified: one characterized by species from continental waters that explore shallow areas at depths of less than 20 m; another one formed by salinity resistant species, distributed through a wide range from the estuary, mostly in the area circumscribed within the isobath range of 10-20 m; and a third one with marine species distributed in areas at depths of 10 m to 50 m.porAcesso AbertoPeixePeixe demersalDiversidadeComunidade (Ecologia)Ecossistema aquáticoSazonalidadeEstuáriosRio AmazonasRio Tocantins - PAPará - EstadoAmazônia brasileiraDissertaçãoCNPQ::CIENCIAS BIOLOGICAS::ZOOLOGIA::ZOOLOGIA APLICADA