LAUSR

A small, interconnected world Countries manage their fisheries as if they were a local resource. To some degree, this may reflect reality, but marine fish, perhaps more than any other vertebrate group, are connected across large distances through ocean currents. Ramesh et al. model how these currents distribute the fish larvae of more than 700 species. They used network analysis to assess the degree to which populations found in one part of the world may have come from another. It seems that global fish populations represent a small-world network where connections across populations are tight and particular hubs of productivity are widely important. Such connectivity has wide-ranging implications for conservation, management, and food supplies globally. Science, this issue p. 1192 Marine fish populations are globally connected such that international fisheries depend on international flows of fish larvae. Fish stocks are managed within national boundaries and by regional organizations, but the interdependence of stocks between these jurisdictions, especially as a result of larval dispersal, remains poorly explored. We examined the international connectivity of 747 commercially fished taxonomic groups by building a global network of fish larval dispersal. We found that the world’s fisheries are highly interconnected, forming a small-world network, emphasizing the need for international cooperation. We quantify each country’s dependence on its neighbors in terms of landed value, food security, and jobs. We estimate that more than $10 billion in annual catch from 2005 to 2014 is attributable to these international flows of larvae. The economic risks associated with these dependencies is greatest in the tropics.