Estudo da alimentação de lithodoras dorsalis (siluriformes, doradidae) na Baía de Marajó, Pará

Abstract

Lithodoras dorsalis is the only species of the family Doradidae that has its body completely covered by plates, which gives it the popular name of stone bacu. When young they have only the series of lateral plates typical of the family, and as they grow the body is gradually covered with additional plates. The present study was based on the analysis of stomach contents of 334 specimens collected in Vigia-PA and Icoaraci-PA between February and December 1995. The fish were captured in a corral (a permanent trap that captures fish with the help of the tide) set in a shallow area off the coast of Marajó Bay. The minimum and maximum lengths obtained were between 14.31- 47 cm. The food items found were classified into 15 categories and the degree of importance of each item in the diet of the species was obtained by the percentage of repletion of each stomach, assessed subjectively on a scale of values from O to 100%. The predominant items during the whole period were of vegetal origin: filamentous algae (35.57%); leaf (27.36%), and fruit (22.77%). The species complements its diet by feeding on mussels (4.12%) and detritus (sand and mud - 5.26%). The opportunistic character of the species is seen in the presence of human waste in its diet (3.44%). The composition of algae, leaf and fruit in the diet of the stone bass was quite similar among seasons; the composition of each item in winter, summer and transition seasons were: algae -35.0% 43.5% and 53.0%; leaf 30.0%, 27.0% and 17.8%; and fruit 22.8%, 15.6% and 16.1%, respectively. This catfish presents a predominantly herbivorous feeding habit, but with an omnivorous and opportunistic character.