Abstract Trophic plasticity is a distinctive feature of freshwater fishes, representing an essential strategy for fish living in resource-variable environments. We analyzed the stomach contents of individuals sampled in two Atlantic Forest streams to identify the primary food sources consumed by Psalidodon aff. fasciatus and verify the existence of spatial, seasonal, and ontogenetic variations. The diet was determined by analyzing the stomach contents using the Volume Method to quantify the importance of food items. In general, Psalidodon aff. fasciatus was classified as an omnivorous species, consuming mainly insects, plant material, and filamentous algae. The results also showed significant effects for all factors considered (spatial, seasonal, and ontogenetic). Finally, Psalidodon aff. fasciatus demonstrated considerable trophic plasticity, which can result in better use of available resources in the environment and improved resource partitioning, reducing intraspecific and interspecific competition. fishes resourcevariable variable environments aff spatial seasonal variations items general species insects material algae (spatial ontogenetic. . ontogenetic) Finally partitioning competition

ABSTRACT We evaluated how seasonality affects the frequency and intensity of fin-nipping, as well as the fish prey preferences of Serrasalmus maculatus Kner, 1858. The study took place in a small reservoir of the Ribeirão Claro River basin, state of São Paulo, southeastern Brazil. Fish were sampled monthly from July 2003 to June 2004, using gillnets. Sampling consisted of leaving 50 m of gillnets in the water for approximately 24 hours each month. No seasonal variation in the frequency and intensity of fin-nipping was observed. Among six prey species, piranhas displayed less damage in their fins, possibly due to intraspecific recognition. Under natural conditions, the caudal fins of Cyphocharax modestus (Fernández-Yépez, 1948) were the most intensively mutilated, which suggests multiple attacks on the same individual. The size of individuals in this species was positively correlated with the mutilated area of the fin, whereas no such correlation was observed for Astyanax altiparanae Garutti & Britski, 2000 and Acestrorhynchus lacustris (Lütken, 1875). The high number of mutilated fish under natural conditions strongly suggests that the relationship between S. maculatus and its prey is more akin to parasitism than to predation. If mutilated fins negatively affect the ability of prey to swim, the spread of S. maculatus might result in an unnatural impact on prey fish assemblages and population structure after damming.

Abstract The widespread use of tubular sections in regions like Western Europe and North America in addition structural and aesthetical reasons can be attributed to the high degree of development of their production technology. Despite this fact their use in Brazil in the past was limited to a few spatial roofs. Currently, the situation in the Brazilian market begins to change caused by the significant increase in the availability of structural hollow sections. This work presents an analysis of "KK" joints with circular hollow sections. A comparison between the analytical design formulations proposed by the Eurocode 3 Part 1.8, the 2nd edition of the CIDECT tubular joint design guide was performed. A finite element model was developed in the ANSYS program for each analysed joint typology. The modelling of a spatial truss made of circular hollow section elements was also performed to enable a comparison between a single joint and the response of the joint as a part of a full scale truss structure.