Ecological carrying capacity of Konosirus punctatus, Coilia nasus, Liza haematocheila of stock enhancement in Oujiang estuary based on Ecopath model

Ecological capacity assessment is an important prerequisite for fishery resource restoration and conservation. Based on the survey data of the Oujiang estuary fishery resources and ecological environment survey in March, May, August and November 2021, the Ecopath model consisting of 24 functional groups was constructed to analyze the trophic level structure and energy flow and calculated the ecological carrying capacity for Konosirus punctatus, Coilia nasus and Liza haematocheila. The results showed that the trophic level of the Oujiang estuary ecosystem ranged from 1.00 to 3.55, the trophic level of K. punctatus (2.46), C. nasus (2.97) and L. haematocheila (2.44) were lower than other fish. The evaluation of the ecosystem structure and function showed that the total primary production/total respiration (TPP/TR) was 2.276, connectance index (CI) and system omnivory index (SOI) were 0.367 and 0.217, respectively. The results indicated that most of the trophic in the ecosystem were not utilized, the primary productivity utilization efficiency was low, and the system was still immature. The current ecological carrying capacity for K. punctatus, C. nasus and L. haematocheila was 0.0189, 0.0379 and 0.0055 t/km², and the potential ecological carrying capacity, based on the Ecopath model, was estimated at 0.070, 0.065 and 0.132 t/km². When reaching the ecological carrying capacity, the TPP/TR, CI and SOI changed marginally. The stability and structure of the ecosystem of Oujiang estuary were not altered significantly, the system has a potential for continuous enhancement.