The fish that launched a thousand ships, then disappeared

A recent analysis clinches the growing evidence that the North Atlantic is a unique region of the world ocean, and helps explain both its special vulnerability to fishing, and perhaps also its fundamental importance in the historical expansion of European influence around the globe.

This is a big fish tale. Scientifically speaking, the body size of an organism is recognized as a “master variable” that is central to understanding most ecological processes, from feeding and movement of individuals to the workings of whole ecosystems. In the oceans specifically, body size is an important predictor of a fish’s vulnerability to fishing (not a surprise to any fisherman). Fisher and colleagues conducted a global analysis of more than 12,000 fish species, and found that a striking concentration of the world’s large fish species live (or lived) in the North Atlantic (see the map, which shows maximum body size, averaged across all fish species in each region).

The most famous of these is, of course, cod, huge quantities of which nourished and motivated the Basques, Vikings, and subsequent European explorers, to strike out across the Atlantic, and begin the European expansion that deeply molded the face of world civilization. The cod population collapsed spectacularly in the 1980s and has been a shadow of its former glory ever since.  The peculiar combination of low diversity, large size, and consequent ‘slow’ life history of cod and the other fishes of the North Atlantic region may help explain why. These characteristics also help explain an otherwise puzzling difference in vulnerability between North Atlantic fisheries, several others of which have similarly declined, and those of the north Pacific, where generally smaller, faster growing species predominate, and fisheries have been more stable. In the North Atlantic, the primeval big ones have got away.

[Original source: Fisher JAD, Frank KT, Leggett WC. 2010. Global variation in marine fish body size and its role in biodiversity–ecosystem functioning. MARINE ECOLOGY PROGRESS SERIES 405:1-13.]