Ichthyoplankton DNA metabarcoding: challenges and perspectives

DNA metabarcoding has been widely used to access and monitor species. However, several challenges remain open for its mainstream application in ecological studies, particularly when dealing with a quantitative approach. In a from the Cover article in this issue of Molecular Ecology, Cédric et al. (2021) report species-level ichthyoplankton dynamics for 97 fish species from two Amazon river basins using a clever quantitative metabarcoding approach employing a probe capture method. They clearly show that most species spawned during the rainy season when the floods started, but interestingly, species from the same genus reproduced in distinct periods (i.e., inverse phenology). Opportunistically, Cédric et al. (2021) reported that during an intense hydrological anomaly, several species had a sharp reduction in spawning activity, demonstrating a quick response to environmental cues. This is an interesting result since the speed at which fish species can react to environmental changes, during the spawning period, is largely unknown. Thus, this study brings remarkable insights into basic life history information that is imperative for proposing strategies that could lead to a realistic framework for sustainable fisheries management practices and conservation, fundamental for an under-studied and threatened realm, such as the Amazon River basin.