The cascading effect of fishing down marine top predators in the northeastern Mediterranean Sea
2025
Konstantinos Touloumis | Athanassios C. Tsikliras | Donna Dimarchopoulou
Abstract Both overexploitation and sea warming have been linked with smaller observed somatic sizes of fish and invertebrate species over time. Overfishing large predators has also been shown to cause cascading effects across food webs. Here, we focused on the Aegean Sea, a major fishing ground of the eastern Mediterranean and a warming hotspot, to investigate changes in the mean size of commercial marine fishes and invertebrates (as approximated by the mean trophic level of the catch), as well as any related top-down cascading effects on the food web or sea warming effects. Our analyses revealed a steady decline of the overall mean weighted trophic level of the Aegean catch from 1982 to 2020, indicating the overexploitation of large, high trophic level, predatory organisms that led to increases in intermediate trophic levels, and subsequent declines in low trophic level species. Any individual or additive effects of overexploitation and climate change on marine populations may affect the structure of ecosystems in unpredictable ways, jeopardizing the health of valuable marine resources and the sustainability of fishing operations. Analyzing historical local patterns may inform future management advice that should aim at using previous knowledge to mitigate the negative effects of anthropogenic pressures on the natural environment.
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