1 These studies show that fisheries are overexploiting both the last refuges for many fish species and species with less resilience [28] and [29], a point we examine in the following two sections. Once considered a vast cornucopia for a hungry world, the productivity of most of the open ocean is more akin to a watery desert. Ryther [30] was one of the first to quantify the scarcity of production to support large deep-sea fisheries. Using measurements of primary productivity and simple ecological rules about food chain trophic efficiency, he calculated that continental shelf fisheries in the western North Atlantic were unsustainable. Little

attention was paid to his conclusion, however, and what had essentially become a fish-mining operation took 30 years to collapse. Shelf fisheries elsewhere also declined, so by 1999, 40% of the world’s major trawling grounds had shifted offshore [12] and [31]. Relatively little primary production per unit area occurs in most BGB324 price of the oceanic epipelagic zone, and its food energy may pass through GSK-3 activation several trophic levels as it sinks, with a rapid decline in biomass before reaching the benthos. This varies,

however, with season and region, and recent work is increasing our understanding of flux of production from the surface to the seafloor [32]. Nonetheless, the combination of low epipelagic productivity and high rates of loss in the water column with increasing depth makes the vast majority of oceanic seafloor energy- and nutrient-scarce. Much of the deep ocean is seemingly featureless (but, in places, species-rich) mud punctuated by isolated “oases” of high biomass supporting a diverse benthic and demersal fauna. Hydrothermal vents and cold seeps that rely on chemosynthetic primary production apparently have little or no interest for fisheries,

but topographic features such as seamounts, mid-ocean ridges, banks, continental slopes and canyons can support commercially valuable Ribonuclease T1 species because these features modify the physical and biological dynamics in ways that enhance and retain food delivery [33] and [34]. Some commercially targeted species form dense breeding aggregations over deep-sea structures, further increasing biomass concentrations, allowing large catches over some seamounts. Rowe et al. [35] calculated that a bottom fishery in 100 km2 of the deep central Pacific would produce no more than 200 kg annually, a minuscule quantity compared to the 8000 t of orange roughy (Hoplostethus atlanticus, Trachichthyidae) caught on average each year over the 30 years of that fishery [36]. Therefore, the success of large-scale deepwater fisheries depends upon regional- or local-scale production processes. This emphasizes, at very least, the need for site-specific information and a precautionary approach as the footprint of fisheries expands. In the deep sea, despite the apparent higher levels of productivity over seamounts and similar features, species cannot support high levels of exploitation.