Abstract
There is rising concern over the future states of marine ecosystems, with multiple drivers interacting and putting pressure on resources. Understanding the future of these systems is becoming increasingly important in the drive to safeguard marine resources for future generations. Despite the increasing complexity of predictive models, their reliability in predicting the future of marine ecosystems remains restricted. Scenarios can be used as a tool to provide plausible narratives of how the future might look, potentially allowing fisheries managers to mitigate some impacts before it is too late. In this study an indicator-based framework has been used, which has previously proven successful in assessing states and trends in marine ecosystems. The Southern Benguela ecosystem was assessed under increased primary production conditions that are considered plausible in the future of the ecosystem. Based on modelled increases in biomass of species within the ecosystem under these conditions, scenarios were tested to see whether it may be possible to increase fishing pressure while maintaining ecosystem wellbeing. Three model scenarios were assessed: increasing fishing on selected prey species, predatory species and both predators and prey. Decision trees were used to assess ecosystem trends, while ANOVAs were conducted to assess the end state of the ecosystem under each scenario. The results suggest that under increased primary production conditions it may be possible to increase fishing pressure on prey species while maintaining, or possibly even improving, ecosystem state. In terms of the prey, and the predator and prey scenarios, some contrasting results were observed. While an increased number of declining indicator trends were observed in these scenarios, the end state analysis did not paint such a negative picture. However, declining trends in indicators cannot be ignored, and caution would need to be taken if fishing pressure was to be increased as in these scenarios.
Highlights
The futures of marine ecosystems are unclear, with the potential effects of drivers such as fishing, climate change, shipping, and pollution remaining largely unknown
Under this scenario there were no significant trends in either biomass or Trophic level of modeled community (TLmc), while there was a moderate increase in the proportion of predators
While fishing pressure and primary production (PP) were not increased in this scenario, the underlying environmental conditions and the maintained fishing pressure would both have somewhat impacted indicator trends
Summary
The futures of marine ecosystems are unclear, with the potential effects of drivers such as fishing, climate change, shipping, and pollution remaining largely unknown. There is, potential for scenarios to provide an insight into possible futures, allowing policy makers and stakeholders the opportunity to mitigate some negative effects and avoid reaching worst-case scenarios. Scenarios involve both drivers within (e.g., fishing pressure) and outside (e.g., environmental change) management control
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