14 research outputs found
Spatial and temporal distribution of fish larvae in marginal lagoons of Pantanal, Mato Grosso State, Brazil
Helminth fauna of Astyanax fasciatus Cuvier, 1819, in two distinct sites of the Taquari River, SĂŁo Paulo State, Brazil
Reproductive biology of Hyphessobrycon eques (Characiformes: Characidae) in Southern Pantanal, Brazil
Abstract Population and reproductive aspects allow the knowledge and understanding of population dynamics and the influence of environmental factors, in addition to ensure the success of a species continuity. Thus, the aim of this study was to analyze population and reproductive traits of the species Hyphessobrycon eques in southern Pantanal, Brazil. Monthly samplings were conducted from February/2009 to January/2011, with 617 individuals analyzed, being 365 females and 262 males. A similar form of distribution in length and weight between the sexes was observed. There was no significant variation in sex ratio over time, with higher proportion of females during the entire sampled period. Both sexes presented a angular coefficient of Weight/Length (b) relationship greater than 3, with speed of increase in weight greater than in length. For females, a long reproductive period was observed, with greater reproductive intensity from January through June. No significant correlation was observed between the Gonadosomatic Index (GSI) and the average temperature, rainfall and river level, despite the fact that reproductive activity occurs in autumn/winter, when there are favorable conditions due to flooding. The size at first maturation (L50) was 20.2 mm, with confidence interval varying from 19.7 through 20.7 mm. The average fecundity was 191.9 oocytes/females and was significantly related to the standard length and total weight (g), demonstrating a relation with energy accumulation to invest in reproduction. The long reproductive period, intensified by partial spawning, higher proportion of females and low L50, show that the species has strategies necessary for survival and rapid population growth, common in small species characterized as r-strategists
REGIME TĂRMICO EM ĂGUAS CORRENTES E SUA IMPORTĂNCIA NA ESTRUTURA DO HABITAT E NA BIOLOGIA DE ORGANISMOS AQUĂTICOS
O regime tĂ©rmico em ĂĄguas correntes e os processos responsĂĄveis por sua variabilidade, sĂŁo de grande importĂąncia ecolĂłgica. Uma vez que a temperatura da ĂĄgua influencia a distribuição, reprodução, crescimento e desenvolvimento dos organismos aquĂĄticos, alĂ©m de produzir efeitos sobre o metabolismo ecossistĂȘmico. Nesta perspectiva, este trabalho revisou os aspectos relevantes Ă variabilidade tĂ©rmica de ĂĄguas correntes, os fatores que os influenciam e sua importĂąncia na estrutura do habitat e na biologia de organismos aquĂĄticos. Com este propĂłsito, observou-se que flutuaçÔes na temperatura da ĂĄgua podem ocorrer naturalmente devido Ă s condiçÔes atmosfĂ©ricas, topografia, descarga e condiçÔes do leito ou por perturbaçÔes antrĂłpicas, tais como, represamento, desmatamento e mudanças climĂĄticas. A heterogeneidade tĂ©rmica ocorre desde escalas locais em gradientes verticais de temperatura da coluna de ĂĄgua, bem como em escalas regionais ao longo do gradiente longitudinal. FlutuaçÔes temporais da temperatura tambĂ©m sĂŁo evidentes e ocorrem diariamente (hora do dia) e sazonalmente (estaçÔes do ano). Tanto espacial quanto temporalmente, a estabilidade (ou variabilidade) da temperatura depende da descarga do rio. A temperatura da ĂĄgua influi diretamente nas condiçÔes do habitat provocando alteraçÔes nas reaçÔes quĂmicas, reduzindo as concentraçÔes de oxigĂȘnio na ĂĄgua, formando barreiras tĂ©rmicas, entre outros efeitos. Tais condiçÔes podem causar elevação da taxa de crescimento de plantas aquĂĄticas, desequilĂbrio no perĂodo de eclosĂŁo de ovos (principalmente de peixes), aumento Ă suscetibilidade a doenças, alterando, desta forma, o funcionamento do ecossistema. Portanto, torna-se evidente a importĂąncia da temperatura da ĂĄgua como fator relevante no controle ambiental de ĂĄguas superficiais
Spatial distribution of fish assemblages along environmental gradients in the temporary ponds of Northern Pantanal, Brazil
Ten temporary ponds in northern Pantanal were studied in July 2006 to explore whether a spatial distribution pattern existed in the composition of fish assemblages, and to identify which environmental variables determined their distribution. The existence of any spatial pattern was tested using the multivariate Mantel correlogram, while the influence of environmental variables was quantified by a Canonical Correspondence Analysis (CCA). A total of 8735 individuals was sampled from 29 species, predominantly represented by <em>Hyphessobrycon elachys</em> and <em>Serrapinnus calliuru</em>s. Composition of fish assemblages varied among ponds, but this variation had no significant spatial pattern for any of the distance classes considered, thus indicating that the species composition varied independently of the distance between ponds. This suggests that stochastic dispersal processes did not influence the spatial structure of species, as predicted by the neutral theory. Conversely, species composition in the ponds was determined by variables that included depth, macrophyte richness and cover. Species such as <em>Markiana nigripinnis</em>, <em>Crenicichla vittata</em> and <em>Moenkhausia sanctaefilomenae</em> occurred in deeper waters, while <em>Parauchenipterus striatulus</em>, <em>Eigenmannia trilineata</em> and P<em>sellogrammus kennedyi</em> were mainly associated with greater richness and macrophyte cover, as already demonstrated by the niche theory applied in ponds which tended to have similar characteristics and a similar fish composition