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, Mariac 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 floods, although similar to 20% also spawned mainly during the receding period and some other year-round, but interestingly, species from the same genus reproduced in distinct periods (i.e., inverse phenology). Opportunistically, Mariac 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 understudied and threatened realm, such as the Amazon River basin.

Automated summary

This study utilizes DNA metabarcoding to analyze ichthyoplankton dynamics in two Amazon river basins, revealing the reproductive behaviors and environmental responses of fish species. The results demonstrate differences in reproductive timing among different species and highlight the rapid response of fish to environmental changes. The findings of this study are important for proposing strategies for sustainable fisheries management and conservation.