Fuzzy comprehensive evaluation of seawater quality of Larimichthys Crocea mariculture areas in Zhoushan, China

Context. Aquaculture is an essential industry and assessing its impact on the environment, particularly water quality, is crucial for sustainable practices. This study aimed to comprehensively evaluate the seawater quality in the Dongji Island yellow croaker (Larimichthys crocea) aquaculture area by using the fuzzy comprehensive evaluation method and field survey. Aims. The main objective of this study was to assess the seawater quality in the aquaculture area during 2 consecutive years (2019 and 2020) on the basis of monitoring data. Methods. The researchers utilised the fuzzy comprehensive evaluation method to assess seawater quality in the Dongji Island yellow croaker aquaculture area. Seawater monitoring data from 6 months in 2019 and 6 months in 2020 were collected for the evaluation. The method included an annual average evaluation, and membership degrees were calculated for each year and individual months. Qualitative interviews with 30 local fish farmers were conducted to unravel the challenges faced by aquaculture water quality management. Key results. The evaluation results indicated that the seawater quality in the aquaculture area was classified as Class I water in both 2019 and 2020 on the basis of the annual average evaluation. However, the membership degrees for 2019 were higher than those for 2020, suggesting that water quality was better in 2019. Furthermore, individual monthly evaluations in 2020 showed varying membership degrees, with May and June having higher membership degrees, indicating better water quality than in other months. August had the lowest membership degree, implying poorer water quality during that month. Conclusions. The study demonstrated that the fuzzy comprehensive evaluation method is effective for evaluating seawater quality in aquaculture areas. It also concluded that the water quality in 2019 was superior to that in 2020, raising concerns about potential environmental degradation. Implications. The quantitative and qualitative findings of this research have important implications for aquaculture practices in the Zhoushan area. The study highlights the need for continued monitoring and management of water quality to ensure sustainable aquaculture practices and adherence to water-quality policies. Future aquaculture endeavours in the region should consider the potential impact on water quality to maintain a healthy ecosystem. © 2024 The Author(s).