American Society of Naturalists

A membership society whose goal is to advance and to diffuse knowledge of organic evolution and other broad biological principles so as to enhance the conceptual unification of the biological sciences.

“Catastrophic mortality, Allee effects, and marine protected areas”

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Emilius A. Aalto, Fiorenza Micheli, Charles A. Boch, Jose A. Espinoza Montes, C. Broch Woodson, and Giulio A. De Leo (Mar 2019)

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Marine reserves help buffer species with Allee effects against catastrophic mortality events


For many species, reproductive failure may occur if abundance drops below critical ‘Allee’ thresholds for successful breeding, in some cases impeding recovery. At the same time, extreme environmental events can cause catastrophic collapse in otherwise healthy populations. Understanding what natural processes and management strategies may allow for persistence and recovery of natural populations is critical in the face of expected climate change scenarios of increased environmental variability. Using a spatially-explicit continuous-size fishery model with stochastic dispersal, parameterized for abalone – a harvested species with sedentary adults and a dispersing larval phase – we investigated whether the establishment of a system of marine protected areas (MPAs) can prevent population collapse as compared to non-spatial management when populations are affected by mass mortality from environmental shocks and subject to Allee effects. We found that MPA networks dramatically reduced the risk of collapse following catastrophic events (75-90% mortality), while populations often continued to decline in the absence of spatial protection. Similar resilience could be achieved by closing the fishery immediately following mass mortalities but would necessitate long periods without catch and therefore economic income. For species with Allee effects, the use of protected areas can ensure persistence following mass mortality events while maintaining ecosystem services during the recovery period.