Are the trophic structure and trophic web metrics of ichthyofauna explained by the environmental conditions of Amazonian streams?

• Grant number: 25/03918-6
• Support Opportunities: Scholarships in Brazil - Master
• Start date: July 01, 2025
• End date: July 31, 2026
• Field of knowledge: Biological Sciences - Ecology - Applied Ecology
• Principal Investigator: Lilian Casatti
• Grantee: Yullia Kaory Shimizu Alves
• Host Institution: Instituto de Biociências, Letras e Ciências Exatas (IBILCE). Universidade Estadual Paulista (UNESP). Campus de São José do Rio Preto. São José do Rio Preto , SP, Brazil

Abstract

The proportion of forest in microbasins and riparian zones plays a structural and functional role in streams. Thus, changes in land use alter the dynamics of aquatic communities, especially fish communities. Amazonian streams on dry land, known as igarapés, have a diverse and endemic ichthyofauna, distributed between preserved environments and environments threatened by human activities, requiring studies that describe how assemblages respond to the complexity of land use. The diet of ichthyofauna is a consistent approach in assessing environmental impacts, with variations in trophic guilds and trophic network metrics used as indicators of environmental quality. In this context, the objective of this project is to evaluate whether and how the trophic structure of fish assemblages is influenced by the conservation conditions of igarapés. To this end, fish, water variables, and habitat variables were collected, which were used to calculate the habitat integrity index (HII) in 28 streams distributed in different conservation situations, 15 inside the Jamanxim National Park (a conservation unit - full protection UC), and 13 in the surroundings marked by soil alterations. The fish will have their stomach contents examined to obtain the Food Index and determine the trophic guilds to which they belong. It will be tested whether the guilds vary according to the position of the streams (interior vs. surroundings) and which environmental characteristics best explain this difference. To determine which factors, species, and guilds are structuring the networks inside and outside the UC, the metrics (nestedness, modularity, connectance, specialization, centrality, and robustness) will be associated with the environmental variables of landscape (percentage of forest in the microbasin) and local (HII), through generalized additive models (GAMs). It is intended that the results of this project will contribute to revealing the conservation status of Amazonian streams, assisting in UC management plans.