Feeding of Pimelodus maculatus Lacépde, 1803 (Siluriformes, Pimelodidae) in the floodplain of the High Paraná River, Brazil

Abstract

Studies carried out in the floodplain of the High River Paraná, from March 1992 to February 1993, aimed to investigate aspects related with the feeding of Pimelodus maculatus Lacépí­¨de, 1803, such as: diet and feeding activity, as well as its variations dependent on the flood pulse and sampling site, and the relationship between the morphology and feeding habit. The diet was assessed using the feeding index (Kawakami & Vazzoler, 1980) over the ocurrence and points frequency (Hynes, 1950; Hyslop, 1980). The average stomach fullness degree (Santos, 1978) and the vacuity index (Albertlni-Berhaut, 1974) were employed as indicators of the feeding activity. The results suggest that this species presents omnivorous-piscivorous behavior. The items were different in its nature (vegetal and animal) and origin (allocthonous and autochthonous) as well as in their size. The basic components of the diet participated in lower or higher rates in different sampling stations and in different periods of the hydrological cycle. The taking and ingestion of an omnivorous diet are apparently adapted to the gill rakers, pharyngeal teeth, stomach and gut. The pattern of feeding activity of P. maculatus exhibited small variations when it was related with the spatial and seasonal (flood pulse). The results related to the diel feeding showed that P. maculatus feeding activity after 8:00 pm, with a peak between 8:00 am and 12:00 noon, decreasing again after this period.