How can mariculture better help feed humanity?

Citation: Olsen Y (2015) How can mariculture better help feed humanity? Front. Mar. Sci. 2:46. The primary production of the marine and the terrestrial domains are similar, ∼49 and 56 Gt C year −1 , respectively (Field et al., 1998), and the marine primary production must likely be more readily available for grazing animals because it is primarily in the form of unicellular phytoplankton. We harvest the ocean quite efficiently, perhaps beyond its sustainable yields (Marra, 2005), and it is therefore surprising that only some 2% of human food are from aquatic systems, including marine and freshwater aquaculture and fisheries (Figure 1A, faostat3.fao.org and fao.org/fishery/statistics/en). This number is valid for total weight based food production. For animal meat and for animal products totally (milk and egg included), the aquatic food acquisition is more important, contributing 34 and 12%, respectively, of the total production in terrestrial and aquatic systems (Figures 1A–C). The combined production of global aquaculture in the sea and in freshwater is currently similar to that harvested from the sea (Figure 1B). As much as 96% of the plant production is from marine aquaculture, or mariculture, whereas 44% of the total fish production is cultured. Fish is totally dominant in freshwater aquaculture (>99%). The production of seaweed has increased most rapidly over the last two decades (Olsen, 2011, fao.org/fishery/statistics/en) and the production is presently similar to the sum of mollusks, crustacean and fish (Figure 1C). The production of mollusk has also increased rapidly while crustaceans and fish that need to be fed have increased slower over many decades. There is already a relatively severe limitation in the availability of feed resources of marine origin needed for fish and crustaceans, because almost all species maintained in intensive production are provided with some marine resources in their feed (Tacon and Metian, 2008). Agricultural plant products have gradually been included in feed for fish and shrimps over the last two decades, now representing a substantial type of resources in the feed for these carnivores (Olsen, 2011). It is an ultimate challenge and question if agriculture can supply the food needed by the increasing global human population in the 21st Century, reaching 9.5 (8.3–10.9) billion by 2050 (UN, 2012a), a population showing a steadily increasing buying power. Among the main concerns is supply of freshwater (Oki and Kanae, 2006; Duarte et al., 2009), availability of phosphate as fertilizers (Cordell and White, 2014), new …