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In Dead Water

The Sea – One of the Largest Food Factories on the Planet

Figure 1:The World’s marine fisheries have stagnated or slightly declined in the last decade, offset only by increases in aquaculture production (Source FAO, 2006).

The World’s oceans provide one of the largest (not domesticated) food reserves on the planet. Overall, seafood provided more than 2.6 billion people with at least 20 per cent of their average per capita animal protein intake (FAO, 2006). Capture fisheries and aquaculture supplied the world with about 106 million tonnes of food fish in 2004, providing an apparent per capita supply of 16.6 kg (live weight equivalent), which is the highest on record (FAO, 2006). Capture fishery production has, however, remained static, and it is only the rise in aquaculture, now accounting for 43% of the total consumption, that  enabled this increase (FAO, 2006).

Worldwide, aquaculture has grown at an average rate of 8.8 per cent per year since 1970, compared with only 1.2 per cent for capture fisheries in the same period. Despite fishing capacity now exceeding current harvest four-fold, marine capture has declined or remained level since 2000, reflecting over-harvest in many regions (Hilborn et al., 2003; FAO, 2006). A major reason why the decline has not become more evident is likely because of advances in fishing efficiency, shift to previously discarded or avoided fish, and the fact that the fishing fleet is increasingly fishing in deeper waters.

Figure 2:Estimated per cent of the global catch taken at depths for the years 1950, 2000 and 2004, which illustrates how fishers are moving further offshore (and often deeper) to catch fish.  
Figure 3:The state of the World’s fishery stocks.

The overall decrease in landings is mostly related to declines in fishing zones in the Southeast and Northwest Pacific oceans (FAO, 2006). In addition, the living resources in the World’s oceans, including those so essential to mankind, are not randomly or evenly distributed. They are largely concentrated in small regions/areas and hotspots, of which continental shelves and seamounts – under-water mountains – play a crucial role. The safety of the World’s oceans as a food source for future generations is however insecure. Over the last decades, there has been continuing exploitation and depletion of fisheries stocks. Undeveloped fish reserves have disappeared altogether since the mid-1980s. During the last decades, there has been a continued decline in fish resources in the ‘developing’ phase, and an increase of those in the depleted or over-exploited phase.

This trend is somewhat offset by the emergence of resources in the ‘recovering’ phase (Mullon et al., 2005; FAO, 2006; Daskalov et al., 2007). There is little evidence of rapid recovery in heavily harvested fish populations, except, perhaps herring and similar fish that mature early in life.  An investigation of over 90 different heavily harvested stocks have shown little, if any, recovery 15 years after 45–99% reduction in biomass (Hutchings, 2000). This is particularly true as most catch reductions are introduced far too late (Shertzer et al., 2007). Indeed, marine extinctions may be significantly underrated (Casey and Meyers, 1998; Edgar et al., 2005). More importantly in this context is not the direct global extinction of species, but the regional or local extinctions as abundance declines. Local and regional extinctions are far more common than global extinctions, particularly in a dynamic environment like the oceans.