Marine protected areas (MPAs) can help manage marine resources, but their effects can vary. A study looked at how fishing pressure before protection affects MPA outcomes. By comparing fish sizes in MPAs and non-MPAs in Southern California, they found that areas with high fishing pressure before protection showed bigger increases in fish sizes after protection. This was seen in species targeted by fishing, but not in non-targeted species. The study suggests that considering pre-closure fishing pressure can help predict and improve MPA effectiveness.