Como a complexidade estrutural e a turbidez afetam o consumo de diferentes tipos de presas?

• Autor(a) principal: Figueiredo, Bruno Renaly Souza
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/4937
• topic: Characiformes, Characidae (Pisces) - Interações tróficas - Complexidade estrutural e turbidez; Peixes - Interação presa-predador; Ecossistemas aquáticos - Lagos - Estabilidade; Ciências Biológicas; Ecologia

Understanding the potential effects of habitat structural complexity and turbidity on prey survivorship is becoming increasingly important, because the human activity has altered the system by modifying the whole trophic dynamic, which has forced changes in the water state, from clear water dominated by submersed macrophytes to turbid waters without plants. Furthermore factors like turbidity and structural complexity should affect the capture efficiency of visual predators, and thereby influence the predator ? prey interaction. On the other hand, inherent characteristics of the prey may facilitate the detection of them by predators, such as body size, and thus also influence the effect of environmental variables. For example, larger prey can be more easily detected than smaller ones. In this context, we performed a factorial experiment using mesocosms to manipulate the habitat structural complexity (presence / absence of submersed vegetation), water turbidity (clear water and turbid water) and prey type (Chironomidae e Cyprididae). In the experiment, it was tested the hypothesis that the interaction between habitat complexity and turbidity decreases the predation depending on prey type. The prediction is that predation becomes maximum in the treatment without plant in clear water, and on the chironomids. A native small fish was used as predator (Moenkhausia forestii) and the dependent variable was the percentage of individuals consumed at the end of the experiment. A factorial analysis of variance showed that the interaction between structural complexity and turbidity was not dependent of the type of prey. On the other hand, the strength of the effect of structural complexity was most conspicuous on smaller preys, and in clear water. Turbidity similarly affects both preys, and in turbid water, the presence of submersed macrophytes did not increase the consumption of prey. Finally, predation may be similar in turbid water without vegetation, and in clear water dominated by aquatic plants, indicating that visual and physical refuge may have the same efficiency as shelter for preys in alternative stable states.