Supporting policy development by determining a fishery’s Safe Operating Space (SOS)

Large changes to the Lake Kinneret ecosystem have occurred since the mid-1990’s including a dramatic crash of the commercial fisheries in 2008, notably the most commercially valuable Sarotherodon galilaeus. Aside from its high market value, S. galilaeus plays an important role in the food web in maintaining water quality. In an attempt to sustain the S. galilaeus population compensatory lake management strategies have been implemented and include stocking millions of S. galilaeus fingerlings every year. Large lake level fluctuations have however inhibited efficient fisheries management due to the impact of factors such as lake shore vegetation and substrate on S. galilaeus reproductive success and on additional ecosystem services. Given the lake level fluctuations and their impact on the ecosystem, questions have been raised regarding the correct policy required to sustain a viable commercial fisheries while accounting for variations in lake level and environmental conditions. Ecopath with Ecosim food-web models of the lake were developed, tested and implemented for the lake as tools for testing management strategies. We expanded on these models and developed an Ecospace model of the lake taking advantage of the recently implemented temporal-spatial framework to simulate the varying environmental conditions and multiple anthropogenic stressors acting on the food web and especially S. galilaeus. Based on scenario testing, we used the models to evaluate and define a management Safe Operating Space (SOS) for S. galilaeus in the lake by varying multiple stressors over a wide range of possible levels. The outcome of the multiple scenarios highlight the range of anthropogenic actions that will ensure a sustainable fisheries.