Tuesday, September 28, 2010

Is the Future to be Jellyfish?

Compass Jellyfish, Chrysaora hysoscella
Reduction in the numbers of fish due to commercial fishing activities combined with changes in climate mean that blooms of the Cnidarian subphylum Medusozoa (jellyfish) are becoming more frequent and more numerous (Mills, 2001 Hydrobiologia 451pp. 55–68). While Ctenophores are also on the increase (see here), the physical size of the larger Medusozoa pose a variety of problems for various industries, both direct marine and non. 
Common Jellyfish, Aurelia aurita
Lynam et al. (2006, Current Biology 16 pp. R493-R494) report on blooms of large jellyfish (>13 cm in diameter, such as Chrysaora hysoscella) in the heavily fished area of northern Benguela off the coast of Namibia, where jellyfish biomass (12 million tonnes) now exceeds that of fish (3.6 million tons). This increase has manifested itself in burst fishing nets, blockage of power station coolant intakes and blockage of alluvial sediment suction used in diamond suction. Similar nuisances are reported by Nagata et al. (2009, Pan-American Journal of Aquatic Sciences 4 pp. 312-325) in Southern Brazil where artisanal prawn fishermen noted shortening the duration of trawl hauls, displacement of hauls to areas further away from the landing ports and the necessity of changing to other fishing gear types.
Lion’s Mane Jellyfish, Cyanea capillata

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