This study investigates the potential of using environmental DNA (eDNA) from seawater samples to detect marine fish biodiversity. The researchers collected seawater samples from a temperate marine ecosystem in Denmark and isolated eDNA using next-generation sequencing. They identified eDNA from 15 different fish species, including both commercially important and rarely recorded species, as well as four bird species. The eDNA approach outperformed or was comparable to conventional methods used in marine fish surveys, demonstrating its effectiveness in monitoring marine biodiversity. Additionally, an experiment on eDNA degradation showed that even small fragments of eDNA can be detected for only a few days, indicating that detectable DNA is likely of local origin. The study provides strong evidence that eDNA can be a valuable tool for monitoring marine biodiversity and resources, with potential applications in fisheries management and conservation.This study investigates the potential of using environmental DNA (eDNA) from seawater samples to detect marine fish biodiversity. The researchers collected seawater samples from a temperate marine ecosystem in Denmark and isolated eDNA using next-generation sequencing. They identified eDNA from 15 different fish species, including both commercially important and rarely recorded species, as well as four bird species. The eDNA approach outperformed or was comparable to conventional methods used in marine fish surveys, demonstrating its effectiveness in monitoring marine biodiversity. Additionally, an experiment on eDNA degradation showed that even small fragments of eDNA can be detected for only a few days, indicating that detectable DNA is likely of local origin. The study provides strong evidence that eDNA can be a valuable tool for monitoring marine biodiversity and resources, with potential applications in fisheries management and conservation.