Spatial Expansion of Fisheries
As part of our collaboration with National Geographic on the Seafoodprint of fisheries, we illustrated and quantified the pace of spatial expansion of fisheries globally since 1950 (see W. Swartz, E. Sala, S. Tracey, R. Watson and D. Pauly, 2010 PLoS one 5(12):e15143). Essentially, the seafoodprint is the oceanic Primary Production Required (PPR) to generate the catch of fisheries, similar to the grass that would be required per year to generate a certain production of milk or meat (see D. Pauly and V. Christensen, 1995, Nature, Vol. 374 Pages 255-257). Here, we used estimates of the Primary Production Required (PPR) to support fisheries catches, to analyze the geographical expansion of the global marine fisheries from 1950 to 2005 (see figure 1). We used multiple threshold levels of PPR as percentage of local primary production to define ‘fisheries exploitation’ and applied them to the global Sea Around Us dataset of spatially-explicit marine fisheries catches. This approach enabled us to assign exploitation status across the 0.5o latitude/longitude Sea Around Us ocean grid system and trace the change in their status over the 56-year time period. This result highlights the global scale expansion in marine fisheries, from the coastal waters off North Atlantic and West Pacific to the waters in the Southern Hemisphere and into the high seas . The southward expansion of fisheries occurred at a rate of almost one degree latitude per year, with the greatest period of expansion occurring in the 1980s and early 1990s (see figure 2). By the mid 1990s, a third of the world’s ocean, and two-thirds of continental shelves, were exploited at a level where PPR of fisheries exceeded 10% of PP, leaving only unproductive waters of high seas, and relatively inaccessible waters in the Arctic and Antarctic as the last remaining ‘frontiers.’ The growth in marine fisheries catches for more than half a century was only made possible through exploitation of new fishing grounds. Their rapidly diminishing number indicates a global limit to growth and highlights the urgent need for a transition to sustainable fishing through reduction of PPR.
Figure 1. Primary Production Required (PPR) to sustain global marine fisheries landings, expressed as percentage of local primary primary production [High resolution].
Figure 2. Time series of areas exploited by marine fisheries by latitude, expressed as a percentage of the total ocean area. ‘Area exploited’ is defined as regions where primary production required (PPR) to sustain reported fisheries landings is greater than 10% of local primary production (PP) [High resolution].