Variações temporais e ontogenéticas na alimentação de Pimelodus britskii Garavello & Shibatta, 2007 em um reservatório neotropical

Abstract

Most fish species has the capacity to change the composition of the diet over time and during different stages of growth. Thus, the objective was to investigate the diet of Pimelodus britskii Garavello & Shibatta, 2007 and evaluate their temporal and ontogenetic changes in the reservoir of Salto Santiago, Iguaçu river, Paraná, Brazil. For both, samples were taken using gill and trawls nets from 2003 to 2010. The determination of the diet was made by the methods of frequency of occurrence and the volume. To assess the importance of food items, these were combined index for food. It was possible to identify broad-spectrum food, 24 food items, but showing a predominance of fish, which allowed its classification as a piscivorous. However, for conducting evaluations and ontogenetic time, these items were grouped into seven categories: algae, detritus, insects, microcrustaceans, plants, fish and other invertebrates. In diet of P. britskii predominated fish in most years, except for 2009, where insects were more significant in the diet, and changes in diet were most noticeable regarding the proportions of consumption secondary items. In 2003 and 2009, it was evident the use of a spectrum range of resources, while 2007 and 2008 accounted for less variability food. Thus, significant variations were found in the diet between the years evaluated. Among the size classes, it was found that the smaller individuals had more diverse diet, consuming mainly detritus and insects, with the growth of individuals identified the trend toward greater specialization of diet with increased consumption of fish, variations being observed significant ontogenetic diet. In general, variations in the availability of food resources, mainly due to the activities of operation of the dam, have been instrumental in the variations in the diet of the species.