Antarctic Sanctuary: fishing effort responses to an international MPA in the Southern Ocean

Abstract While the impacts of marine protected areas (MPAs) are widely studied, empirical evidence on MPAs established beyond national jurisdiction remains limited. This study provides the first ex-post assessment of how fishers adjusted their effort in response to the establishment of the world’s largest international MPA in the Southern Ocean. The study examines compliance with regulations designed to deter fishing effort around the MPA boundary and how fleets in the area adapted their fishing patterns after its establishment. Using high-resolution vessel tracking data and exploiting quasi-random variation induced by the geographical boundaries of the MPA, we find that the implementation of the MPA led to between 64% and 73% reduction in fishing effort around its boundaries. Since target species remained unchanged and catch volumes and limits were largely stable in this region, the main consequence of the MPA appears to be the displacement of fishing effort to areas surrounding its boundaries. Using vessel-level data over the periods before and after the establishment of the MPA, we also find limited evidence that vessels operating near the MPA before its implementation exited the fishery or significantly adjusted their overall operation hours at sea. Instead, these vessels reduced fishing hours while increasing non-fishing activities at sea, compared to vessels operating under comparable conditions. Our results suggest that effective MPA compliance can be achieved in international waters where sovereign fishing states compete over shared resources, while it may increase fishing costs in the short run due to the loss of historical fishing grounds.