The distance between where marine fish are caught and where they are consumed has been steadily increasing since the 1950s, finds a study in Nature Communications. Continued expansion of fisheries by the same rate into the next century is unlikely to meet future global demand.

Population increases and the expansion of global trade over the past century have created an increasing demand for fish as a source of protein. Technological improvements in the efficiency of fishing fleets have enabled this expansion, although the extent to which the world's oceans are able to support this demand in the future is unclear.

Reg Watson and colleagues analysed global fisheries catch data collected by the Food and Agriculture Organisation, and find that the distance between sourcing and consumption of fish has increased steadily each year between 1950 and 2011. By comparing the energy required to produce this volume of fish, with levels of ocean productivity (derived from satellite data), they find that this increase has required a greater proportion of the ocean's annual production over this period of time.

Projecting these trends to the year 2100, they conclude that if catch rates remain static, as they have in the past decade, then only an expansion of the marine fish farming industry will be able to meet future food demands. However, this sector is also likely to face challenges to reduce the proportion of marine-sourced fishmeal used to feed larger, predatory species such as farmed salmon.