DOI: 10.5061/dryad.n2z34tn82
title: Data from: Metabarcoding versus species-specific primers to estimate <em>Salmo trutta</em> biomass and density in mountain streams

description: Environmental DNA (eDNA) is a cost-efficient, non-invasive method to
 monitor fish populations, but the quantitative aspect of this technique
 (e.g., estimating biomass or densities) remains underexplored. Few studies
 have established relationships between fish DNA concentration and
 biomass/density. Here, we investigate the relationship between eDNA
 concentration (copies per liter) and trout biomass and densities estimated
 by electrofishing in mountain streams of Picos de Europa National Park
 (Spain). We assessed eDNA effectiveness in inferring biomass/density using
 18S rRNA (18S) and cytochrome c oxidase I (COI) metabarcoding, and
 quantitative PCR with a COI-specific Salmo trutta primer, each performed
 with different datasets from the same sampling points. Salmonidae eDNA
 concentration positively correlates with trout biomass and density. Both
 18S and specific-COI markers showed a significant increase in DNA
 concentration as trout biomass and density rose in electrofishing surveys.
 However, general COI did not exhibit significant trout DNA concentration
 and biomass/density relationships, despite providing greater taxonomic
 resolution at the species level. Further analysis exploring eDNA
 concentration and biomass/densities across different trout size classes
 (fry, juvenile, and adult) revealed that juvenile trout biomass
 contributed the most to the observed eDNA concentration – biomass/density
 relationship. Our results suggest that DNA concentration estimated from
 metabarcoding, when using an appropriately selected primer, can reliably
 indicate trout biomass and density in these mountain streams where trout
 is the dominant species. Although quantitative PCR showed similar trends,
 it had lower explanatory power. This study highlights the importance of
 integrating a quantitative framework in metabarcoding for ecological
 monitoring and biodiversity assessments. Factors such as amplicon length,
 genetic region, marker specificity, or fish size class can influence the
 relationship between sequencing reads and electrofishing data. This
 methodology could aid the conservation and management of fish populations
 and other communities, though further research is needed to extend these
 results and assess eDNA detection reliability.
description: # Data from: Metabarcoding versus species-specific primers to estimate
 *Salmo trutta* biomass and density in mountain streams Name: Alba M. Losa
 Institution: Instituto de Hidráulica Ambiental, Universidad de Cantabria
 Email: [albamaria.losa@unican.es](mailto:albamaria.losa@unican.es) ##
 Files The dataset is organized into several files:
 **ASVtable_COI2019_13sites.xlsx:** ASV table for fish taxa and
 corresponding taxonomy (18S dataset). **ASVtable_EUKA2018_13sites.xlsx:**
 ASV table for fish taxa and corresponding taxonomy (COI dataset).
 **qPCRSpecificPrimerData_13sites.xlsx:** Raw qPCR data for specific
 primers. **Electrofishing_data.xlsx:** Biomass and density data from
 electrofishing surveys, including biomass (g/m²) and density
 (individuals/m²). This dataset contains the necessary data to replicate
 linear regression models. ## Data Sources Genetic data were obtained from
 water samples collected between 2018 and 2020. ## Sharing & Access
 This work is licensed under a CC0 1.0 Universal (CC0 1.0) Public Domain
 Dedication license.