Factors determining the structure of fish assemblages in Tarumã River, Jaru Biological Reserve, Machado River drainage, northern Brazil

Abstract

Few studies on fish assemblages and relations with environmental factors in aquatic systems in southeastern Amazonia have been carried out when compared to other areas in the Amazon. Therefore, which are the main environmental variables and processes responsible for structuring them remains unknown. We hypothesized that fish assemblages respond the variation in the physical-chemistry variables between seasons of the hydrological cycle in a pristine river in the Amazon. The study was performed on fish assemblages of the Tarumã River, Jaru Biological Reserve, Rondônia. Samplings were carried out in five sites along the river in March and September, 2015, which included fish collection and environmental data measurements. Principal component analysis was performed to ordinate the sites in high water and low water seasons, according to environmental variables. We used a similarity analysis in order to identify the individual contribution of species in hydrological period and a partial redundancy analysis for quantify the relative importance of environmental variables in the species composition. As predicted by our hypothesis, the species composition was influenced by dissolved oxygen and temperature. Myloplus rubripinnis, Serrasalmus compressus, and S. rhombeus were the most abundant during high water, while S. rhombeus, Myloplus lobatus, Prochilodus nigricans, and Hydrolycus armatus were the dominant species during the low water.

Diversity of freshwater fish at Sago Palm Wetlands, Nakhon Si Thammarat Province, Thailand

“…From this study, we observed that the most important water quality variables affecting fish distribution were temperature, dissolved oxygen, pH, turbidity, orthophosphate, nitrite, nitrate and ammonia. These physicochemical variables also have been identified as important factors in fish assemblages in other tropical rivers (Dubey et al 2012;Zulkafli et al 2018;Rosette et al 2020;Costa et al 2021). Other physicochemical parameters of this lake did not show any significant statistical differences in determining fish distribution.…”