title: Environmental DNA from Seawater Samples Correlate with Trawl Catches of Subarctic, Deepwater Fishes.
abstract: Remote polar and deepwater fish faunas are under pressure from ongoing climate change and increasing fishing effort. However, these fish communities are difficult to monitor for logistic and financial reasons. Currently, monitoring of marine fishes largely relies on invasive techniques such as bottom trawling, and on official reporting of global catches, which can be unreliable. Thus, there is need for alternative and non-invasive techniques for qualitative and quantitative oceanic fish surveys. Here we report environmental DNA (eDNA) metabarcoding of seawater samples from continental slope depths in Southwest Greenland. We collected seawater samples at depths of 188-918 m and compared seawater eDNA to catch data from trawling. We used Illumina sequencing of PCR products to demonstrate that eDNA reads show equivalence to fishing catch data obtained from trawling. Twenty-six families were found with both trawling and eDNA, while three families were found only with eDNA and two families were found only with trawling. Key commercial fish species for Greenland were the most abundant species in both eDNA reads and biomass catch, and interpolation of eDNA abundances between sampling sites showed good correspondence with catch sizes. Environmental DNA sequence reads from the fish assemblages correlated with biomass and abundance data obtained from trawling. Interestingly, the Greenland shark (Somniosus microcephalus) showed high abundance of eDNA reads despite only a single specimen being caught, demonstrating the relevance of the eDNA approach for large species that can probably avoid bottom trawls in most cases. Quantitative detection of marine fish using eDNA remains to be tested further to ascertain whether this technique is able to yield credible results for routine application in fisheries. Nevertheless, our study demonstrates that eDNA reads can be used as a qualitative and quantitative proxy for marine fish assemblages in deepwater oceanic habitats. This relates directly to applied fisheries as well as to monitoring effects of ongoing climate change on marine biodiversity-especially in polar ecosystems.
authors.affiliation: Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Philip Francis
authors.initials: PF
authors.lastname: Thomsen
authors.affiliation: Section for EvoGenomics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Peter Rask
authors.initials: PR
authors.lastname: Møller
authors.affiliation: Section for EvoGenomics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Eva Egelyng
authors.initials: EE
authors.lastname: Sigsgaard
authors.affiliation: Section for EvoGenomics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Steen Wilhelm
authors.initials: SW
authors.lastname: Knudsen
authors.affiliation: Technical University of Denmark, National Institute of Aquatic Resources, Charlottenlund, Denmark.|Greenland Institute of Natural Resources, Nuuk, Greenland.
authors.forename: Ole Ankjær
authors.initials: OA
authors.lastname: Jørgensen
authors.affiliation: Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark.|Department of Zoology, University of Cambridge, Cambridge, United Kingdom.|Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom.
authors.forename: Eske
authors.initials: E
authors.lastname: Willerslev
mesh_terms: D000818:Animals; D001110:Arctic Regions; D004247:DNA / Q000032:analysis*; D005398:Fisheries; D005399:Fishes / Q000502:physiology*; D005843:Geography; D006116:Greenland; D012623:Seawater / Q000032:analysis*
chemical_list: D004247:DNA