Theoretical studies of marine protected areas (MPAs) suggest that more mobile species should exhibit reduced local effects (defined as the ratio of the density inside vs. outside of the MPA). However, empirical studies have not supported the expected negative relationship between the local effect and mobility.
This study evaluates, through modeling, the hypothesis that differential, habitat-dependent movement (i.e. a higher movement rate in the fishing grounds than in the MPA) might explain the disparity between theoretical expectations and empirical results.
The results show that increasing disparity in the habitat-specific movement rates shifts the relationship between the local effect and mobility from negative (the previous theoretical results) to neutral or positive (the empirical pattern). The authors state that this shift from negative to positive occurs when differential movement offsets recruitment and mortality differences between the two habitats.
Therefore, it is underlined that local effects of MPAs might be caused by behavioral responses via differential movement rather than by, or in addition to, reductions in mortality.
It is highlighted that distinguishing effects of movement and demography is especially crucial because movement could lead to misinterpretation about the efficacy of management strategies and their effects on species conservation.
Jiao J, Pilyugin SS, Riotte-Lambert L, Osenberg CW (2018) Habitat-dependent movement rate can determine the efficacy of marine protected areas. Ecology doi: 10.1002/ecy.2477.