Perfil das dietas da ictiofauna dos igarapés da várzea estuarina da baía de Marajó – Pa

Abstract

The estuarine floodplain environment suffers great influence from the daily tide level. Unlike the floodplain areas of the Central Amazon, which are influenced by the elevations and droughts of the river over a longer period, six months. The ichthyofauna in the estuary changes during the different periods (i) flood; (ii) transition and (iii) drought of the Tocantins and Amazon Rivers; presenting species that are exclusively du1ciaqueous in the flood period; estuarine, resident during all the periods in the area and marine species that invade the estuary during the dry period. This variation in species distribution is also reflected in the type of feeding. This study sought to characterize the trophic structures of estuarine communities over the different seasons of the year. Samplings were carried out in three locations along the Marajó Bay, namely: (a) Igarapé Sapucajuba, Belém-PA, innermost portion of the bay; (b) Igarapé Paracuri, Icoaraci-PA, intermediate portion of the bay and (c) Igarapé Anuerá, Vigia- PA, outermost portion of the bay during the months of November 1994 to December 1995. The specimens were fixed, sorted, identified, and deposited in the MPEG fish collection. The biometric data of the specimens were obtained with a 0.5mm pachymeter and for the analysis of stomach contents a stereoscopic magnifying glass was used; a subjective scale based on the degree of stomach repletion was used, with values from 0- 100% of stomach repletion. The food items were grouped into 7 food categories. A total of 7,795 individuals were obtained, distributed among 86 species belonging to 34 families and 11 orders. The stomach contents of only 60 species of this total were analyzed. About 30 species (63%) fed primarily on "aquatic invertebrates", 10 species (17%) fed on "particularized organic matter", 9 species (15%) on "terrestrial invertebrates", 2 species (3%) on "leaves and fruits of terrestrial plants", 1 species was a piscivore. Species feeding on "aquatic invertebrates" were predominant in all three periods of the year, representing about 67% of the fish community.