although a limited number of these collapses may have been caused or exacerbated by natural phenomena for example climate variability human activities and overfishing essentially nonsustainable management are the primary culprits pauly et al it is important to understand that fish constitute not only biomass in the ocean but a potential economic input into society together these two elements imply that fisheries are an economic activity by which fishers can catch fish resources in perpetuity if they are managed sustainably