Researchers detect regime shifts in the Northern Benguela ecosystem caused by increased fishing and climate drivers during the last 50 years.
An Ecopath with Ecosim ecosystem model was, together with Ecological network analysis and Integrated Trend Assessments, used to describe the cumulative impacts of fishing and climate drivers on the structure of the Northern Benguela ecosystem.
Benguela Niños events in 1974 and 1984 led to large fluctuations in primary production. Together with increased fishing pressure and reduced production in the 1980s this led to changes in the internal structure of the ecosystem, impacting the main demersal species.
The sardine and anchovy stocks collapsed, and commercially less viable species have taken over: jellyfish has become the major zooplankton consumer and gobies are now the major prey for most top predators in the system.
Regime shift leading to lower resilience
The researchers summarize that the Northern Benguela ecosystem has moved from a regime with high redundancy and lower internal structure into a system with higher internal structure and less resilience. This reorganized system will need a large shift to change with the consequential change not necessarily being back towards the pre-existing system.
“It is challenging for the fishery industry to adapt to the current situation. In order for the industry not to be taken by surprise by further rapid changes, the next step will be to design management systems where environmental drivers, such as the Benguela Niños, will be taken in to account. This is important not least as climate changes are foreseen to increase in the future” author Maciej Tomczak concludes.