Metabarcoding outperforms traditional electrofishing in decapod and fish inventories, paving the way for enhanced biodiversity monitoring in the Caribbean

Environmental DNA (eDNA) metabarcoding has revolutionized the biodiversity monitoring in aquatic ecosystems, giving access to taxonomic lists in a non-disruptive way. Despite limits (taxonomic resolution nor taxa quantification), the method has repeatedly proved its effectiveness and is now used as routine freshwater monitoring tool. Especially since traditional method, including electrofishing (TEF), are reputed stressful for the species, non-selective and disruptive for the ecosystem, leading to its abandonment in Martinique (F.W.I.) for regular monitoring. The aim of this project was to explore the possibility of using eDNA metabarcoding for the detection of fish and decapods in Martinique streams, by first validating it with TEF. We selected 14 stations, a representative panel of the river diversity, and performed TEF and eDNA to compare both, based on the species richness recovered. Then, from eDNA taxonomic inventories, we assessed the ecological state of the studied stations, using different biodiversity indices (Shannon, Simpson and Bray-Curtis) and investigated how stations abiotic characteristics shape assemblages. Here, we confirmed the eDNA metabarcoding method as a reliable tool for monitoring fish and decapods, confirming most of the taxa caught by TEF and revealing the presence of additional (native and/or invasive) species. We faced some issues in discriminating some genetically close species (e.g. Sicydium sp.) potentially leading to under-representation in community assemblages, but not in functional diversity. Additional efforts are needed to raise standardized protocols, but we encourage stakeholders to join such initiative to shed light on the rich biodiversity in sometimes poorly studied regions and to face invasions.