The past and potential antagonistic effects of fishing ban against nutrient loading control on eutrophication restoration in Lake Hongze
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Abstract
Integrated management strategies are often implemented to achieve comprehensive environmental restoration; however, the potential antagonistic effects among such measures are seldom examined. Fishing bans, aimed at enhancing fish biodiversity, may counteract the effectiveness of nutrient control measures in mitigating eutrophication. This study employs the PCLake model and structural equation modeling (SEM) to evaluate this hypothesis in Lake Hongze, the fourth largest shallow lake in China. The PCLake model was calibrated using observational data from Lake Hongze collected between 2016 and 2020. The calibrated model was subsequently applied in a hindcast analysis from 2020 to 2024 and a forecast simulation from 2025 to 2030 to assess the impacts of fishing bans. Combined with SEM path analysis, the results support the hypothesis that fishing bans can exhibit antagonistic effects on nutrient loading control by enhancing top-down regulation relative to bottom-up processes. Specifically, the fishing ban led to increased fish biomass, phytoplankton abundance, and nutrient levels over the past four years, while reducing the abundance of submerged macrophytes, zoobenthos, and zooplankton. Projections further indicate that such antagonistic effects would persist through 2030 if the fishing ban remains in place as planned. Additionally, model forecasts suggest that even with adjustments to the duration and intensity of fishing bans, antagonistic effects could be amplified under more stringent nutrient control scenarios. This study provides valuable insights into maximizing the net benefits of combined environmental management strategies through a systematic framework that evaluates both the effects and underlying processes of different interventions.
Article activity feed
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Human activity causes many different threats to the environment, which usually lead to a loss of biodiversity, the lifeblood of our ecosystems and food systems (Elouafi, 2024). One of these threats is eutrophication. Although this process can occur naturally under certain circumstances, it is now much more widespread due to the excessive use of fertilizers by humans, causing algal blooms—a phenomenon exacerbated by global warming.
As early as the late 20th century, biomanipulation, artificial intervention in various trophic groups, was proposed as one of the possible solutions to mitigate eutrophication. However, the effectiveness of this method is not obvious, due to the ecological complexity of the systems, which involves indirect effects, feedback mechanisms, and response delays (Benndorf, 1990).
It seems that the simplest form of …
Human activity causes many different threats to the environment, which usually lead to a loss of biodiversity, the lifeblood of our ecosystems and food systems (Elouafi, 2024). One of these threats is eutrophication. Although this process can occur naturally under certain circumstances, it is now much more widespread due to the excessive use of fertilizers by humans, causing algal blooms—a phenomenon exacerbated by global warming.
As early as the late 20th century, biomanipulation, artificial intervention in various trophic groups, was proposed as one of the possible solutions to mitigate eutrophication. However, the effectiveness of this method is not obvious, due to the ecological complexity of the systems, which involves indirect effects, feedback mechanisms, and response delays (Benndorf, 1990).
It seems that the simplest form of biomanipulation is a fishing ban. Qin et al. (2025) studied the effects of a 10-year fishing ban in a subtropical lake, which was implemented to prevent further eutrophication. The research was conducted halfway through the planned fishing ban period and included both a hindcast analysis of the conditions prevailing before the ban and a forecast of the results of the ban in the future.
The results showed that the fishing ban amplified the impact of fish on zooplankton through top-down regulation, while the high abundance of phytoplankton persisted. This indicates that the system shifted toward stronger control by consumers, but without eliminating the enhanced availability of nutrients. The authors predict that the fishing ban may slow down the process of eutrophication restoration due to the intensification of the trophic cascade driven by fish.
Therefore, while restricted fishing ban may be an effective way to preserve high ecological diversity in natural systems, it is not necessarily equally effective as a measure to prevent eutrophication. In this case, Benndorf’s (1990) suggestion might be more applicable, according to which ‘maximum efficiency of food web manipulation as a management tool is achieved at a 'optimum' biomass of zooplanktivorous fish’.
References
Elouafi, I. 2024. Why biodiversity matters in agriculture and food systems. Science 386, https://www.science.org/doi/10.1126/science.ads8197
Benndorf, J. 1990. Conditions for effective biomanipulation; conclusions derived from whole-lake experiments in Europe. Hydrobiologia 200, 187-203, https://link.springer.com/article/10.1007/BF02530339
Qin Bo, Dakos Vasilis, Cai Yongjiu, Zhao Yu, Yang Xiangdong, Zhang Enlou, Wang Rong (2025) The past and potential antagonistic effects of fishing ban against nutrient loading control on eutrophication restoration in Lake Hongze. bioRxiv, ver.5 peer-reviewed and recommended by PCI Ecology https://doi.org/10.1101/2025.10.05.680530
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