Fisheries, the inverted food pyramid
A global assessment of fishing patterns and fishing pressure from 110 different Ecopath models, representing marine ecosystems throughout the world and covering the period 1970 to 2007, show that human exploitation across trophic levels is highly unbalanced and skewed towards low productive species at high trophic levels, which are around two trophic levels higher than the animal protein we get from farming. Overall exploitation levels from low trophic species were less than 15% of production, and only 18% of the total number of exploited groups and species were harvested above 40% of their production. Generally well managed fisheries from temperate ecosystems were more selectively harvested at higher exploitation rates than tropical and upwelling (tropical and temperate) fisheries, resulting in potentially larger long-term changes to the ecosystem structure and functioning. The results indicate a very inefficient utilisation of the food energy value of marine production. Rebuilding overfished components of the ecosystem and changing focus to balancing exploitation across a wider range of trophic levels, ie balanced harvesting, has the potential to significantly increase overall catches from global marine fisheries.