Aspectos ecológicos do cachorro-de-padre Auchenipterichthys longimanus (Siluriformes: Auchenipteridae) em igarapés da Amazônia Oriental, Pará, Brasil

Abstract

The aim of this study was evaluate the ecological aspects related to relative growth, size at first maturity, reproduction, energy investment, sex ratio and diet of the driftwood catfish Auchenipterichthys longimanus (Siluriformes: Auchenipteridae) from the rivers of Caxiuanã National Forest, State of Pará, Brazil. The samplings were carried out bimonthly from July 2008 to July 2009. In this period, 625 specimens of A. longimanus were captured, which 338 were females, 251 males and 36 macroscopically undefined individuals. The results indicated a polyphasic growth pattern for both sexes, and the stanza changing point was about 11.5 cm for males and 12.5 cm for females, values close to the estimated size at first maturity (L₅₀). Through the gonadosomatic index (GSI%) was observed reproductive asynchrony between the sexes, where males had higher values of GSI% in January and the females showed a peak in March. We also emphasize the differences in the energy investment patterns between the sexes and maturity, according to Condition Factor (K). In relation to sex ratio, we observed a higher frequency of females at the reproductive period, suggesting a sexual segregation pattern for reproductive purposes, with the possibility of harems formation or reproductive migration. About the diet, A. longimanus was considered omnivorous, tending to insectivorous. However, in March 2009 the catfish A. longimanus was considered frugivorous due to the high consumption of fuits of Virola surinamensis (Myristicaceae). Because of the high occurrence of allochthonous items, this research highlights the importance of the riparian forest as food source for one of the most abundant fish species in the Caxiuanã region. Since the seeds of V. surinamensis remain intact in the stomach, we evaluate the ecological potential of A. longimanus as a seed disperser, checking the seed feasibility after sowing. Thus, we expect to contribute with the ecological knowledge about A. longimanus, the ecology of the Auchenipteridae family, and also the decision-making concerning politic-environmental questions related to the conservation and management of natural fish populations stocks in one of the largest units of conservation in the State of Pará.