By: Dr. Jeff Drazen
Department of Oceanography
University of Hawaii
The average depth of the oceans is about 4000 meters. Waters greater than 200m cover half the planet making the deep-sea the single largest living space on earth. Despite all this space some of species that live in the deep-sea may not be there long if harvest continues at the current rate.
|Pictures of some deep-sea fish. Some have been renamed to make them more marketable to fish consumers|
|Vertical ecological zones in the deep ocean as organized by ocean depth below the surface. Seawater temperature, light and biomass – aproxy for food available to fishes are also indicated. Source:http://www.soest.hawaii.edu/oceanography/faculty/drazen/Oceanography%20website/|
Given the low productivity of deep-sea fishes and the current demand of many deep water fisheries, exploitation of these species has not proven sustainable. For example, fishing for orange roughy in Tasmania and New Zealand is a ghost of its former self. In fact, many of the seamounts where the fishes were taken now have names like Graveyard or Morgue. Even more, Red Lobster has a franchise-wide ban on serving orange roughy and Chilean seabass because these fish are in such dire straits. The trawling activities used to capture the fishes also destroy their habitats making recovery more unlikely.
|A full trawl net of orange roughy. Source: http://www.southernfriedscience.com/?p=6979|
|How most see deepwater species. Here rattail aka grenadier, as fillets. Source: http://www.alibaba.com/product-gs/356482658/GRENADIER_FISH.html|
Deep water fisheries represent the last frontier in industrialized fishing; however, they are not likely to continue for long. Given the low productivities of deep-sea fish stocks and the poor track record of sustainable fishing, many are calling for a stop. You might ask, why not fish even deeper? The average depth of the ocean is ~4000m and fishing is only occurring to half that depth. The biomass of fishes declines exponentially with depth so that below about 2000m fish abundance is not great enough to harvest economically. It seems we really have reached the bottom of the barrel.
In addition, read here about how a new study revealed severe mismanagement of European deep-water stocks.
Bailey, D.M., Collins, M.A., Gordon, J.D.M., Zuur, A.F., Priede, I.G., 2009. Long-term changes in deep-water fish populations in the northeast Atlantic: a deeper reaching effect of fisheries? Proceedings of the Royal Society B: Biological Sciences 276 (1664), 1965-1969.
Devine, J.A., Baker, K.D., Haedrich, R.L., 2006. Deep-sea fishes qualify as endangered Nature 439, 29.
Drazen, J.C., Haedrich, R.L., 2012. A continuum of life histories in deep-sea demersal fishes. Deep Sea Research I 61, 34-42.
Morato, T., Watson, R., Pitcher, T.J., Pauly, D., 2006. Fishing down the deep. Fish and Fisheries 7, 24-34.
Links for further reading:
Can Ecosystem-Based Deep-Sea Fishing Be Sustained? http://digitalcommons.library.umaine.edu/sms_facpub/145/
Koslow, J. A. 2007. The Silent Deep: the Discovery, Ecology and Conservation of the Deep Sea. The University of Chicago Press.