Study in the ecosystem structure and trophodynamics in the Kuroshio-Oyashio Extension area

Based on the data collected in Kuroshio-Oyashio Extension area (KOE) fishery resources survey in 2023, this document analyzed the trophic structure and characteristics of this pelagic ecosystem using the Ecopath model. Marine living organisms were divided into 25 functional groups based on their ecological characteristics. The results indicated that the trophic levels of these groups ranged from 1.00 to 4.35, with blue shark has the largest trophic level. Mean transfer efficiency of the KOE pelagic ecosystem was 11.08%. The nutrient flow in the KOE pelagic ecosystems is largely driven by grazing food chain. Compared to previous studies in the KOE and its coastal ecosystems, both the total system throughput (TPP, 1942.22 t·km^-2·year^-1) and the total respiration (TR, 250.10 t·km^-2·year^-1) were relatively lower, while the TPP/TR (4.42) was higher. Combined with a low system omnivory index (0.2), the overall ecosystem characteristics suggested that the KOE pelagic ecosystem was at a low level of maturity and vulnerable to disturbance from external activities. Due to the significant important of KOE pelagic ecosystem, we suggest conducting long-term and stable ecosystem level survey and assessment. Meanwhile, we recommend the collaboration work with more biological data to enhance the quality of KOE pelagic ecosystem model.