Comparação de respotas funcionais de duas espécie de peixes píscivoras

Abstract

Species of the Cichla genus have been introduced in a variety of tropical aquatic ecosystems, thus resulting in a marked reduction in diversity and population size of native fish assemblies due to their predatory behavior. Despite Cichla induced impact the mechanisms by which the species are still poorly known. In this study we compared the functional response of an alien predator fish C. kelberi and a native predator H. aff. malabaricus. More specifically, the tested hypotheses were: 1) both predator species have functional responses of type II on different prey species, and 2) the functional responses of the alien predator were higher for all preys when compared to the native predator. The predators were acclimated in tanks of 500 liters and fed twice daily with preys O. niloticus and L.vannamei for 3 days, 4 preys in the morning and 4 in the afternoon. Hunger levels were standardized after a fast of 48 hours. After the pre-experimental phase an exemplar of C. kelberi was randomly introduced in each tank of O. niloticus with initial prey densities of 2, 4, 8, 16, 25 and 40, and for L. vannamei 2, 4, 8, 16, 32 and 64 (n = 4 per density). After 24 hours the number of prey consumed was counted. This method was repeated for the native predator H. aff. malabaricus. Totaling 48 experimental units. The functional response C. kelberi was greater than or equivalent to the native predator H. aff. malabaricus. There was no difference in consumption between the two species at low densities. The attack rate did not differ between the two predators and handling time was driven by C. kelberi for the species O. niloticus. However, the two species showed functional response type II, thus corroborating with the comparative functional response method to predict the impact on native communities. Functional Comparative Response is a quick and reliable method to predict the ecological impacts of invasive species