NATURE ADRIFT 



would be doing well to retain a third of the plankton out of the water we 

 actually tiltcr, but this is a minor point compared with the proportion of 

 water we could handle. The sea is so vast that even a tremendous human 

 effort would seem quite negligible. The whole Gulf Stream, for example, 

 is only a small part of the world's ocean mass, yet as said on page io8 more 

 water flows in the Gulf Stream in a day than in Niagara in three years. 

 There is an anonymous verse which runs: 



If all the sea 

 were one sea 

 That would be 



1 , 3 70,23 2,000,000,000,000,000,000 cc. 



One cubic centimetre is not very much but this figure is equal to 

 301,471,060,000,000,000,000 gallons. If we had 10,000 extremely efficient 

 filtering stations, each deahng with 100 milhon gallons a day it would take 

 about a million years to deal with the equivalent of all the sea water once. As 

 things are at present it pays us far better to let nature takes its own course 

 and let the fish feed on the plankton, even at several stages removed, feeding 

 sometimes twenty-four hours a day and certainly seven days a week, no 

 overhead costs, no labour diflkultics, and then catch the fish even if our 

 present catch is only 0-02 per cent of the ocean's productivity, though we 

 certainly could catch more than we now do by exploiting the world's 

 fisheries more rationally. 



Changes in costs, a product of pharmaceutical value from plankton out 

 of all proportion to its mere food value, or a radically new engineering design 

 are of course all possibilities, and might easily change the arguments used 

 here against the commercial catching of plankton in any indiscriminate way. 



There are, however, several successful commercial ventures for catching 

 plankton which should really be classed as 'fisheries' as are the shrimp 

 'fisheries'. Three examples can be given here: the mysid fishery in hidia, the 

 krill fishery for Megaiiyctipliaiics (Fig. 22; 5) in the Mediterranean, and the 

 fisheries for larger planktonic prawns (Pencidae) in several places in the 

 tropics. Each of these is based on the catching of fairly large Crustacea, some- 

 times attracted by lights, and they are not indiscriminate plankton fisheries. 



It has been said that, as the world's population increases, the need for food 

 will outweigh the pure economics and that plankton wall then need to be 

 caught at whatever cost. With the coming of the atonnc age there may be 

 possibilities, but with conventional power suppli.cs the shortage of fuel would 

 be every bit as important as a shortage of food. 



As an alternative to catching plankton as food, can we artificially enrich 

 the sea to increase the growth of plankton and so increase the tish supply? 



166 



