Spatial and seasonal distribution of fish eggs and larvae in one free-flowing river in the Neotropical savanna.

Abstract

Reproduction is one of the most important biological aspects for the maintenance of viable populations and understanding the spatial and seasonal patterns in the reproduction of Neotropical fish is a point that still needs considerable investigation. In this study, the main aim was to reduce knowledge gaps concerning fish eggs and larvae distribution patterns. For this, we used the River Araguaia basin, one of the main hydrographic basins of the neotropical savanna, as focal point of study. Samplings of fish eggs and larvae were carried across the hydrological regime during flooding and drought events between December 2018 and July 2020 at 15 sites distributed along a 350 km stretch of the River Araguaia basin. Fish eggs and larvae were found in all sampling sites with the highest number of catches in the flood season. The fish larvae were represented by five orders, 22 families, and 22 at the genus or species level. Both environments, tributary and main channel of the River Araguaia, are important for fish reproduction, and no difference was found in the use between the main channel and the tributaries. The results showed that spatial factors are important to explain the change in larval composition, which may have a wide or restricted distribution related to specific habitats. The main factors related to the reproductive activity of fish in this region are the physical and chemical changes in the water that occur in the flood season. These results indicate that the River Araguaia basin has environmental integrity and provides favorable conditions for the reproductive activity of fish, including long-distance migratory species. Considering this, mitigate measures that guarantee the preservation of the natural flow are crucial for the maintenance of fish biodiversity. This article is protected by copyright. All rights reserved.