Assessing fish sampling effort in studies of Brazilian streams

Abstract

Neotropical stream fish assemblages have attracted much scientific attention in recent decades. However, spatial and temporal patterns in sampling, and the types of methodologies being used in studies, remains unclear. Here, we conducted an in-depth review of the published literature on Brazilian stream fish assemblages, recording where and how these surveys were conducted. We found that the number of studies has increased over time, but significant geographic biases remain, with most studies having been conducted in southeastern and southern Brazil. Studies deployed a variety of sampling methods, but we found a growing trend towards the use of the electrofishing, sampling stream lengths of 50 meters, and over a duration of 60 min. Rarefaction curves showed that sampling effort is low in relation to the number of streams sampled in all basins studied, especially in the Amazon, Tocantins Araguaia, Sao Francisco and Uruguay basins, and northeast Brazil. Thus, we emphasize the importance of further surveys in these regions, since even basic parameters for ecological studies and conservation, such as species richness, remain critically underestimated. In light of the recent reductions in public funding for scientific research in Brazil, we also highlight the importance of networks and collaborations between Brazilian ichthyologists to add more value to scientific production and contribute to the greater standardization of data.