Monthly eDNA Metabarcoding Data From the Coastal North Sea Area Align With Fish Species-Specific Life Cycle Events

Abstract

Coastal environments serve as essential nursing, feeding, and spawning grounds for commercially and ecologically important fish species, some of which use nearshore habitats as transitional steps in their ontogenetic migration. Understanding fish communities' spatial and temporal dynamics in coastal habitats is fundamental for sustainable ecosystems and fisheries management. Despite the importance of long-term monitoring to obtain information on fish movements and distribution, fine-scale temporal datasets on fish communities remain scarce due to the intense field work required. In the present study, we explored the use of eDNA 12S metabarcoding of seawater samples to monitor fine-scale temporal and spatial patterns in fish communities. In total, 168 samples were collected across 20 sampling campaigns conducted monthly between August 2021 and August 2023 within the 12 nautical miles of the Belgian part of the North Sea. eDNA patterns revealed no marked temporal or spatial patterns at the community levels due to the ubiquitous presence of the dominant Southern North Sea fish species linked to their non-migratory behavior and use of the coastal Belgian waters as nursing and spawning grounds. However, species-specific temporal patterns reflected their reproductive activity and seasonal migrations. Additionally, fish species spatial distribution was consistent with previous beam trawl and eDNA-based surveys conducted within the Belgian part of the North Sea and was mainly driven by the environmental gradient created by freshwater discharge from the Scheldt estuary. Our findings demonstrate that eDNA metabarcoding is a valuable biomonitoring tool and provides insight into fish distribution, migration, and reproductive activity.