Marine fisheries increasingly operate under conditions that constrain conventional biodiversity monitoring, particularly in observationally constrained environments. Nocturnal light-fishing represents a widespread anthropogenic pressure in such regions, yet its ecological effects on marine vertebrate assemblages remain insufficiently documented. Here, we assess changes in cetacean and fish assemblages associated with light falling-net fisheries by integrating environmental DNA (eDNA) metabarcoding with visual observations and net sampling in the Dongsha waters of the South China Sea. Field surveys were conducted aboard active light falling-net fishing vessels, with eDNA samples collected before and after artificial illumination. Across all methods, 14 cetacean species and 221 fish species were detected. eDNA consistently revealed higher species diversity than conventional approaches. Following illumination, eDNA detections indicated increased cetacean occurrence and fish diversity. Cetacean species count increased from 8 to 12, and fish species count from 121 to 206, together with higher relative read abundance, supporting an aggregating effect of artificial light on marine vertebrates. Local optimization of cetacean primers further enhanced detection sensitivity. Overall, our findings demonstrate that eDNA analysis provides an effective and practical tool for detecting fisheries-associated changes in marine vertebrate assemblages, offering field-based environmental evidence to support the assessment of anthropogenic pressures in data-poor tropical marine ecosystems.
Zhang et al. (Wed,) studied this question.