Feeding and trophic ecomorphology of Satanoperca pappaterra (Pisces, Cichlidae) in the Manso Reservoir, Mato Grosso State, Brazil

The aim of this work was to evaluate the relationship between diet and features of the trophic ecomorphology of Satanoperca pappaterra (Heckel, 1840) in an impacted environment. Samples were collected from March 2000 to February 2003 in Manso Reservoir, Cuiabá River, Mato Grosso State. Analysis of 93 stomachs contents showed that food resources associated with the substrate, such as plant remains, detritus, fish scales and Chironomidae larvae, dominated the diet. Consequently this species was characterized as a detritivorous-invertivorous. However, individuals collected in 2003 showed a greater selection of benthic organisms in relation to previous periods. Morphological structures such as position of the mouth, form of the lips, gill rakers and pharyngeal teeth, in addition to the length of the intestine, showed specializations correlated with the diet. However, as long as the food was associated with the substrate, it seemed to be selected according to its abundance in the environment.<br>O objetivo deste estudo foi descrever e avaliar as relações entre dieta e traços da ecomorfologia trófica de Satanoperca pappaterra (Heckel, 1840) em ambiente impactado. As coletas foram realizadas no reservatório de Manso, MT., entre março/2000 a fevereiro/2003. A análise de 93 estômagos, mostrou que recursos alimentares associados ao substrato, tais como restos vegetais, detritos, escamas e larvas de Chironomidae, predominaram na dieta, caracterizando esta espécie como detritívora-invertívora. Entretanto, indivíduos coletados em 2003 mostraram maior seleção de organismos bentônicos em relação aos períodos anteriores. As estruturas morfológicas, como posição da boca, forma dos lábios, rastros branquiais e dentes faríngeos, além do comprimento do intestino mostram um certo grau de especialização ao tipo de dieta. No entanto, o alimento, desde que associado ao substrato, parece ser selecionado de acordo com sua abundância no ambiente

FISH FEEDING IN BRAZILIAN RESERVOIRS: ALTERATIONS AND CONSEQUENCES IN THE EARLY STAGES OF COLONIZATION.

Com o incremento da construção de barragens nos rios brasileiros nas últimas décadas, houve uma necessidade cada vez mais premente de se entender os efeitos desses impactos sobre a ictiofauna. Neste contexto, a alimentação dos peixes tem merecido destaque, uma vez que está diretamente associada ao processo de colonização. Assim, nesta revisão, são apresentadas as alterações nas fontes de alimento e uso dos recursos alimentares pelos peixes em reservatórios brasileiros, nos primeiros estágios do represamento. Fontes alóctones de alimento, tais como a vegetação inundada e os invertebrados terrestres, são rapidamente incorporadas na dieta dos peixes oportunistas. Já as fontes autóctones (vegetais, zooplâncton, zoobentos e peixes), podem aumentar ou sofrer declínio em suas abundâncias, comprometendo de modo diferente a dieta dos peixes. As maiores alterações estão associadas ao notável incremento do zooplâncton que é capitalizado por peixes filtradores, os quais aumentam extraordinariamente suas populações e ao enorme incremento de peixes forrageiros, os quais sustentam as populações de piscívoros, que usualmente são altamente beneficiadas. T odas estas alterações afetam a estrutura trófica do novo ambiente, causando mudanças temporárias nas cadeias alimentares. Ressalta-se, no entanto, que a maioria dos estudos aqui mencionados foram realizados em curta escala temporal e para respostas mais conclusivas sobre a organização trófica da ictiofauna seria necessário um acompanhamento de médio a longo prazo nos ambientes represados.    With the increased of dam constructions in Brazilian rivers during the last few decades, it has been necessary to understand their impacts on the fish fauna. Fish feeding behavior is directly associated with the reservoir colonization process. Thus, in this review paper we show the changes in food sources and their use by fish in Brazilian reservoirs during the early stages of colonization. Food allochthonous sources, such as flooded vegetation and terrestrial invertebrates, are quickly used by opportunistic fishes. Availability of autochthonous sources (plants, zooplankton, zoobenthos and fishes) may increase or decrease, changing the fishes diet of different ways. The greatest alterations are the notable increase of zooplankton which is capitalized by filtering fishes, increasing extraordinarily their populations; and the enormous increase of the forage fishes, which usually lead to an increase in abundance of piscivores. These changes affect the trophic structure in the new environment, leading to temporary changes of the food web. However, most studies cited in this review paper were conducted over a short temporal scale. To reach more conclusive answers about the trophic organization of the fish fauna, monitoring programs encompassing middle to long term scales in the impoundments are recommended

Fish habitat associations along a longitudinal gradient in a preserved coastal Atlantic stream, Brazil

Habitat conditions at multiple scales are one of the major factors structuring ichthyofauna. Thus, we analyzed the fish habitat associations along the headwater-mouth gradient of a coastal Atlantic stream. We categorized the sampling sites into habitat units, so that in the middle reach these categories were statistically differentiated into riffles, runs and pools. Samplings were carried out quarterly from May 2009 to February 2010 using electrofishing. Principal component analysis (PCA) indicated an environmental gradient from higher water velocity and rocky bottom to deeper and sandy areas in the headwater-mouth direction. A total of 1,495 individuals belonging to 27 species were captured, being 13, 18 and 22 from headwater, middle and mouth reaches, respectively. Shannon diversity was slightly higher in the middle reach, while beta diversity showed higher rates of addition than turnover in species along the longitudinal gradient. Fish structure, evaluated by DCA (detrended correspondence analysis) scores, showed significant differences between upper reaches and mouth reach, but the middle riffles did not differ from headwater habitats. In the middle reach, mesohabitat analysis distinguished riffles, with higher abundance of fast-water crenuchids, from pools, with a higher abundance of lentic-water characids. These results suggest that environmental differences along the stream determine the wider structural patterns. However, the middle reach amassed species from upper areas and lowlands in structured fish mesohabitat associations, possibly implying distinct local ecological interactions. These findings contribute to the assessment of stream conservation status and to recognize eventual direct impacts on fish structures along longitudinal gradients