Studies on the trophic structure of fish give information on species autoecology and their role in the ecosystem. The aims of this study were to characterize the diet of Serrapinnus notomelas in small streams of the River Machado basin and to assess the effect of rainfall seasonality. Fish were collected bimonthly from July 2013 to May 2014 with seine nets and hand nets. The length of each specimen was measured to identify category classes. There were also measured the fullness index and volume of each ingested item, and these data were combined to obtain an alimentary index. We used ANOVA and Kruskal-Wallis to test for differences between length classes and fullness index, Chi-squared tests to detect seasonal differences in origin of food items and non-metric multidimensional scaling analysis to examine temporal variation in diet. We found that most of the specimens were longer than 20 mm, showing a polymodal distribution. In both seasons stomachs of most fish were full. Serrapinnus notomelas feeds on items of plant and animal origin. A higher consumption of aquatic macrophytes and algae was observed, suggesting omnivorous feeding behavior with a tendency to herbivory. Items of plant and autochthonous origin were consumed more than other items in both seasons, and consumption of animal and autochthonous items varied between seasons. These results reinforce the idea that S. notomelas show trophic plasticity between seasons. KEYWORDS: Characidae, Trophic ecology, Igarapés, Ornamental fish, Amazon. Ecologia alimentar de Serrapinnus notomelas (Characiformes: Cheirodontinae) em igarapés da bacia do Rio Machado, Rondônia, Brasil RESUMOEstudos sobre a estrutura trófica de peixes dão informações sobre autoecologia espécies e seu papel no ecossistema. Os objetivos deste estudo foram caracterizar a dieta Serrapinnus notomelas em igarapés da bacia do rio Machado e avaliar o efeito da sazonalidade das chuvas. Os peixes foram coletados bimestralmente de julho 2013 a maio de 2014, com redes de arrasto e redes de mão. O comprimento de cada espécime foi medido para identificar a categoria das classes. Também foram medidos o grau de repleção e o volume de cada item ingerido, e estes dados foram combinadas para se obter um índice alimentar. Foram utilizados uma ANOVA e Kruskal-Wallis para diferenças entre classes de comprimento e graus de repleção, teste de qui-quadrado para detectar diferenças sazonais na origem dos alimentos e análise de escalonamento multidimensional não-métrico para examinar variação temporal na dieta. Nós encontramos que a maioria dos indivíduos eram maiores que 20 mm, apresentando distribuição polimodal. Para ambas as estações a maioria dos estômagos apresentaram-se cheios. Serrapinnus notomelas ingeriu itens vegetais e animais. Observamos maior consumo de macrófitas aquáticas e algas, sugerindo comportamento alimentar onívoro com tendência a herbivoria. Itens de origem vegetal e autóctone foram mais consumidos que os demais itens em ambas as estações, e o consumo de itens animais e itens autóctone...
In one year, 76 first generation (F1) Brazilian sardine Sardinella brasiliensis breeders spawned 84 times spontaneously in captivity. This is the first report for the genus Sardinella. Following the pattern found in the natural environment, the number of spawns, as well as fertilization and hatching rates were higher in spring, summer and fall than in winter. Until now, winter spawning was only presumed to occur in a natural environment. Water temperature, and not photoperiod, was positively correlated with reproductive performance.
Abstract:Igarapés are Amazonian streams that are extremely susceptible to environmental changes. Due to the rapidly occurring riparian land use changes, and the several impacts these may have on fish assemblages, it is highly valuable to describe and understand the current relationships between these assemblages and the local environmental conditions, especially in barely know areas. In this research, we studied the taxonomic composition and fish assemblage attributes variation in three streams with different riparian conservation conditions: forest, intermediate and pasture. Samplings were performed every two months from October 2011 to September 2012, in three 1 st order streams in the Machado River Basin, Rondônia. Fish were collected using trawls (seine net with a mesh size of 2 mm) and dip nets (2 mm mesh) along the entire stretch; the obtained samples were preserved and identified per site type. A total of 2 141 fish specimens belonging to 59 species, 17 families and five orders were recorded. Unlike the intermediate and pasture streams, the forest stream showed a high richness and low abundance. The forested stream exhibited the highest diversity and evenness value, and had low dominance, unlike the other streams. The variance partitioning and partial Redundancy Analysis (pRDA) indicated that assemblage composition was significantly explained by the environmental variables such as: depth, water velocity, pteridophytes and grasses, but not by spatial predictors. The non-metric multidimensional scaling (NMDS) analysis showed that intermediate and pasture streams separated from the forested stream. We concluded that both, the stream environmental variables and fish assemblage attributes were influenced by the different conservation status and land cover. Given the influence of regional processes, which have a pervasive role in local fish assemblages, land use at the watershed scale is important, especially to explain the higher richness and diversity found in forested streams. Rev. Biol. Trop. 65 (1): 103-115. Epub 2017 March 01.Key words: complexity, conservation, richness, fish assemblages.Tropical rainforest streams are nutrientpoor streams with a dense forest cover that prevents light from reaching the water surface (Walker, 1995). Their biological and physicochemical features are therefore greatly influenced by the surrounding vegetation (Mendonça, Magnusson, & Zuanon, 2005). They are also considered to be extremely vulnerable to environmental impacts, such as land-use change by agricultural purposes, which may cause environmental degradation (Dembkowski & Miranda, 2012) and influence aquatic vertebrate fauna (Miserendino et al., 2011).Physicochemical habitat characteristics are considered to be highly relevant factors affecting the distribution of species and the organization of communities in streams (Hoeinghaus, Winemiller, & Birnbaum, 2007). Variations in species composition, structure and distribution in fish assemblages has been attributed to area (i.e. basin area, lake surface area), regional net...
Monosex female jundiá (Rhamdia quelen) generated through indirect sex reversal may have their growth influenced by the stocking density, which is an important factor for production in fish farming. Since zootechnical data from R. quelen offspring generated by crossbreeding between genotypic masculinized females (neomales) and normal females were never reported, the objective of this study was to compare the zootechnical indexes of neomale and normal male offspring stocked at densities of 500, 1,000 and 1,500 fish m-3 (D1, D2, and D3) for 61 days. The initial mean weight and length of the neomale and normal male offspring were 0.90 ± 0.12 g / 4.94 ± 0.22 cm and 0.80 ± 0.12 g / 4.60 ± 0.37 cm, respectively. A completely randomized experimental design with three replicates was used, with fish stocked in 0.07 m³ tanks. At the end of the experimental period, the data evaluated showed that there were no significant differences between progeny or among stocking densities in terms of survival, weight, weight gain, length, feed conversion or feed consumption. Therefore, neomale offspring presented adequate productive performance during the juvenile stage and tolerated increases in stocking density without performance loss, making the neomales suitable for R. quelen cultivation.
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