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With the objective of evaluating the influence of the environmental integrity on feeding, condition factor and reproduction of Phalloceros harpagos, the species biology was analyzed in the Tarumã Stream micro-basin, Naviraí, Mato Grosso do Sul State (upper Paraná river). Samples were collected from 2007 to 2010, and biometric data of specimens was registered. Stomach and gonad were taken for the analysis of feeding and reproduction, respectively. The species is detritivore, showing a high flexibility in the diet. Debris and sediment, followed by plant and algae were the most ingested items. As for the condition factor, no definite pattern was observed in the values for both sexes, probably because the species has a long reproductive period. The frequency of occurrence distribution of gonad maturity stages indicated a greater number of immature females in the dry season at one of the least impacted sites. On the other hand, in the most affected site females were observed with increased fecundity. From the results obtained, it was found that the different levels of environmental degradation have no significant influence on feeding and condition factor, but rather probably exert influence on the reproduction of the species.

In this study, it was examined the reproductive biology of Astyanax. altiparanae, in streams with different levels of environmental disturbance in the Ivinhema river basin (Mato Grosso do Sul State, Brazil). Samplings were conducted between July 2001 and November 2011, at 101 sites, using sieves, seining nets, gill nets and electrofishing. Streams were classified into three levels of environmental integrity. We analyzed 735 specimens, 410 females and 325 males. Females predominated in impacted streams and both sexes presented nearly the same pattern of length distribution in the three levels of environmental integrity. Females reached gonadal maturity with greater lengths (L50 = 55.67mm) in altered and impacted streams and had higher reproductive activity between October and December. The species showed higher Condition Factor and higher reproductive intensity in the impacted streams. Our results evidenced that in impacted sites the species exhibited a good ability to allocate a significant portion of its energy to reproduction, probably due to the greater supply of food.

This study aimed at analyzing the influence of different levels of environmental integrity of streams of the Ivinhema river basin (Mato Grosso do Sul State, Brazil) on the diet of A. altiparanae. Samplings were performed from July 2001 to November 2011 at 101 sites, using sieves, seining and gill nets, and electrofishing. Streams were classified into three levels of environmental integrity. We analyzed 664 stomachs with the methods of frequency of occurrence and volumetric analysis index, combined in the Importance Index (AI). The species was omnivorous, with predominance of allochthonous resources. At the least impacted sites, the most representative resource was allochthonous plant material; and in the altered sites in the rainy period the most consumed item was allochthonous arthropods. On the other hand, at the most impacted sites in the dry period there was a lower consumption of allochthonous plant material and allochthonous arthropods, compared with other levels of environmental integrity considered, with higher consumption of autochthonous arthropods. The results evidenced that in the least impacted sites there was greater contribution from allochthonous resources, probably because these environments show a more preserved riparian forest.

O objetivo deste trabalho é descrever a variação sazonal do fator de condição e do ciclo de desenvolvimento gonadal de Pimelodella cf. gracilis no rio Amambai, Estado de Mato Grosso do Sul. O comprimento e o peso de 232 indivíduos foram obtidos para cálculo do Fator de Condição Alométrico. Para as fêmeas (n=162), obtivemos, ainda, o peso e o estádio de maturação dos ovários, para cálculo do IGS e da freqüência percentual desses estádios em cada estação do ano. Os resultados obtidos indicam que os maiores valores de IGS correspondem às estações primavera e verão. Com base nisso, conclui-se que o período de desova da espécie está compreendido entre os meses de outubro e abril, embora não tenha sido possível determinar com maior precisão quando esse evento ocorre. Os maiores valores do fator de condição foram observados no verão, como possível conseqüência damaior atividade alimentar que os indivíduos apresentaram durante a primavera. The aim of this study is to describe the seasonal variations ofcondition factor and of the gonadal development cycle of Pimelodella cf. gracilis in Amambai River (MS, Brazil). The length and weight of 232 individuals were measured to calculate the Allometric Condition Factor. For the females (n=162), we also obtained the ovarian weight and the gonadal maturity stages in order to calculate the GSI and the relative frequency (%) of this stages at each season of the year. Results indicate that the highest GSI values were registered in spring and summer. Thus, we concluded that the spawning season of this species occurs between October and April. However, it was not possible to identify more precisely when this event occurs. The highest values of condition factor were observed in summer, as a probable consequence of the more intensive feeding activity thatindividuals demonstrate during the spring.

Esse estudo teve como objetivo descrever a dieta e analisar a atividade alimentar de Pimelodella cf. gracilis no rio Amambai, Estado de Mato Grosso do Sul, ao longo das quatro estações do ano. Para tanto, analisou-se o conteúdo estomacal e calculou-se o Índicede Repleção Estomacal de 232 indivíduos. Os resultados obtidos demonstram que essa espécie é onívora e generalista, pois consome itens alimentares de origens diversas, tais como material vegetal, insetos terrestres e aquáticos, moluscos, escamas de peixes, sedimentos e material não-identificado. Apesar disso, o item material vegetal foi predominante na dieta ao longo de todo o ano, demonstrando que, embora onívora, essa espécie apresenta tendência à herbivoria. A dieta básica mostrou variações sazonais em sua composição, pois observou-se que alimentos alóctones têm sua importância aumentada nas estações mais quentes e chuvosas. Além disso, também foram registradas alterações sazonais na atividade alimentar, possivelmente influenciadas por fatores climáticos (temperatura e pluviosidade) e fisiológicos (ciclo reprodutivo).The aim of this study is to describe the diet and the feeding activity of Pimelodella cf. gracilis in Amambai river, Mato Grosso do Sul State, Brazil, along the four seasons of the year. For this, the stomach contents of 232 individuals were analyzed and their Stomach Fullness Index was calculated. The results indicate that this species is omnivorous and generalist, so it consumes feeding items of several origins, such as plant material, terrestrial and aquatic insects, mollusks, fish scales, sediments and non-identified material. Notwithstanding this, the plant material was predominant in the diet along the whole year, indicating that Pimelodella cf. gracilis tends to herbivorous habit. The composition of the basic diet changedseasonally, so we observed that allochthonous items have their importance increased in the warm and rainy seasons. Besides this, we also observed seasonal shifts in the feeding activity, probably due to climactic (temperature and precipitation) and physiological factors(reproductive cycle).

This study analyzed physicochemical characteristics of the water, degradation of the surroundings and the influence of these factors on the diet of two fish species of Astyanax in Tarumã stream microbasin, central western Brazil. Fish were collected in eight sites between 2007 and 2010, using gillnets and sieves. Environmental variables were evaluated by a principal component analysis and the diet based on Spearman’s correlation. The variables width, type of riparian vegetation, pH, conductivity, total dissolved solids, temperature, oxidation and reduction potential, presence of waste, and altitude have separated the sampling sites into two groups: ‘less impacted’ and ‘more impacted’. The two characid species presented omnivorous habit, typical of disturbed environments. The consumption of food resources was different over the space: terrestrial plants and sediment were more important in the most impacted sites for both species. And specifically to Astyanax altiparanae the order of importance of the food was distinct between most and less impacted sites. These data indicated that the diet of these species is a suitable tool for analyzing the environmental quality of the studied sites.

Dentre os trabalhos que objetivam o estudo da condição de peixes com o uso do método alométrico (K=W/Lb), não há um consenso sobre o procedimento mais adequado para o cálculo do coeficiente b, pois alguns autores utilizam um coeficiente constante para todas as sub-amostras (estações do ano, por exemplo), enquanto outros calculam um valor de b para cada sub-amostra. Com a intenção de demonstrar qual desses procedimentos é mais adequado, este trabalho verificou-se que a utilização de um valor de b para cada sub-amostra provoca distorções nos valores do Fator de Condição. Conclui-se, então, que o método que calcula o coeficiente b a partir do agrupamento de todos os indivíduos e o utiliza com um valor constante para todas as sub-amostras é, dentre os dois procedimentos testados, o mais adequado para estudo da condição de peixes.

O objetivo deste trabalho é descrever a variação sazonal do fator de condição e do ciclo de desenvolvimento gonadal de Pimelodella cf. gracilis no rio Amambai, Estado de Mato Grosso do Sul. O comprimento e o peso de 232 indivíduos foram obtidos para cálculo do Fator de Condição Alométrico. Para as fêmeas (n=162), obtivemos, ainda, o peso e o estádio de maturação dos ovários, para cálculo do IGS e da freqüência percentual desses estádios em cada estação do ano. Os resultados obtidos indicam que os maiores valores de IGS correspondem às estações primavera e verão. Com base nisso, conclui-se que o período de desova da espécie está compreendido entre os meses de outubro e abril, embora não tenha sido possível determinar com maior precisão quando esse evento ocorre. Os maiores valores do fator de condição foram observados no verão, como possível conseqüência da maior atividade alimentar que os indivíduos apresentaram durante a primavera.

Esse estudo teve como objetivo descrever a dieta e analisar a atividade alimentar de Pimelodella cf. gracilis no rio Amambai, Estado de Mato Grosso do Sul, ao longo das quatro estações do ano. Para tanto, analisou-se o conteúdo estomacal e calculou-se o Índice de Repleção Estomacal de 232 indivíduos. Os resultados obtidos demonstram que essa espécie é onívora e generalista, pois consome itens alimentares de origens diversas, tais como material vegetal, insetos terrestres e aquáticos, moluscos, escamas de peixes, sedimentos e material não-identificado. Apesar disso, o item material vegetal foi predominante na dieta ao longo de todo o ano, demonstrando que, embora onívora, essa espécie apresenta tendência à herbivoria. A dieta básica mostrou variações sazonais em sua composição, pois observou-se que alimentos alóctones têm sua importância aumentada nas estações mais quentes e chuvosas. Além disso, também foram registradas alterações sazonais na atividade alimentar, possivelmente influenciadas por fatores climáticos (temperatura e pluviosidade) e fisiológicos (ciclo reprodutivo).

This study aimed to describe the diversity of fish parasites in the Amambai River, in the Mato Grosso do Sul State, and generate information to facilitate studies of the biotic integrity of the region. During the period of September 2015 and July 2015, 48 specimens of 11 species of fish were analyzed for parasites. A total of 56.25% of the fish sampled from the Amambai River were infected with one or more metazoan species. A total of 21,514 parasite specimens belonging to 24 different species we found; they were distributed among six groups: Acanthocephala (Neoechinorhynchida), Cestoda (Proteocephalidea), Crustacea (Ergasilidae), Digenea (Cladorchiidae, Dadaytrema), Monogenea (Dactylogyridae) and Nematoda (Atractidae, Cucullanidae, Camallanidae, Rhabdochonidae). Of these, a monogenean, Mymarothecium sp. and four nematodes – Cucullanus sp.; Procamallanus (Spirocamallanus) inopinatus Travassos, Artigas, and Pereira, 1928; Rabdochona acuminate (Molin, 1860); and Rondonia rondoni Travassos, 1920 – were recorded for the first time on new hosts. This is the first work to gather information about the parasite fauna of fish from Amambai River in the Mato Grosso do Sul State, and provides records that contribute new reports of the occurrence of parasites in new locations.

Changes in diet of Laetacara araguaiae Ottoni and Costa, 2009 were evaluated in the Sucuriú River (Upper Paraná basin, Brazil) in an area with a small hydroelectric power plant, both before and after the formation of the reservoir, in order to answer: Did the construction of the reservoir affected the diet of this species? The results showed greater change of diet composition in the upstream section of the reservoir. It was observed that before the formation of the reservoir and the first year after, the individuals from upstream section formed a group characterized by an insectivorous diet. With the dam construction and habitat change we observed that aquatic plant material, sediment, and algae predominated in the diet. These results show the opportunistic feeding habit of L. araguaiae and contribute to the understanding of how the impoundment of rivers can influence the trophic dynamics of the ichthyofauna.

Em estudos sobre alimentação de peixes, é prática comum determinar a dieta de uma espécie com base na análise do conteúdo estomacal. Para a realização destes estudos normalmente são aplicados os métodos de ocorrência, numérico, volumétrico e gravimétrico. A utilização destes métodos, entretanto, nem sempre é possível, e o objetivo deste trabalho é propor uma metodologia alternativa baseada na atribuição de pontos aos itens alimentares a partir da obtenção da massa total e de uma simples inspeção visual dos conteúdos estomacais