Species identification and biomass assessment of Gnathanodon speciosus based on environmental DNA technology

Environmental DNA (eDNA) technology has emerged as a valuable tool for monitoring species distribution, assessing aquatic biodiversity and fish biomass. This study aimed to investigate the relationship between eDNA and the biomass of Gnathanodon speciosus (G. speciosus) using quantitative Polymerase Chain Reaction (qPCR) technology. Specific primers were designed for the target species. Water samples were collected from three differently-sized aquariums located at Qingdao Polar Ocean Park between July 2022 and March 2023. The results demonstrated a modest correlation between total biomass and eDNA concentration (Pearson, r = 0.74, p < 0.05). However, a significant positive correlation exists between biomass per unit volume and eDNA concentration per unit volume (Pearson, r = 0.87, p < 0.05). The study also examines the influence of environmental factors, such as salinity, and different growth parameters characterized by body weight and fork length, on eDNA concentration. The univariate linear regression analysis indicated that body weight and fork length exerted a notable influence on eDNA concentration. No significant relationship was observed between salinity and eDNA concentration (ANOVA, p > 0.05). This preliminary study lays the groundwork for monitoring and assessing the biomass of G. speciosus. This study also provides valuable insights into quantifying the relationship between environmental DNA and biomass, establishing a crucial theoretical framework for future assessments of open-sea fisheries resources through environmental DNA analysis.