PLANKTON AS FOOD 



The body fluids of fish and plankton niostly contani much less salt 

 than sea water, and so can be taken to increase the water content of the 

 body. Fish juices are probably fairly reliable but plankton juices less so 

 because of the very varying nature of plankton. Plankton is good food, 

 high in protein and fat cemtent, perhaps not so good as fish either physically 

 or psychologically, but limited amounts, if fish cannot be obtained, would 

 help to eke out an existence and increase the chances of a successful rescue. 

 'Eke out' is probably a suitable phrase, as, even if abundant, plankton would 

 not be safe to eat in quantity because of the possibility of excesses of nauseat- 

 ing or unpalatable flavours and over-rich fats and vitamins which in excess 

 can be fatal. Some plankton, even if fish is plentiful, would be advisable 

 in the diet of the shipwrecked mariner because it does contain some of the 

 vitamins, especially 'C, which are lacking in tish, although fish livers in 

 particular contain ample vitamin 'A'. 



Unfortunately, the best catches would be made at night (p. 155) 

 when it is too dark to see what is happening and to sort out the catch, but 

 nevertheless plankton is there, and to have a small net for catching it might 

 make all the difference between hfe and death. Dr. Bombard survived for 

 sixty-five days, drifting from the Canaries to the West hidies. He had no 

 rain for twenty-three days; he drank sea water for the first fourteen and 

 fish juices for forty-three, and his plankton diet kept up his vitamin supply. 

 It cannot be said that it was a pleasure trip and he suffered very greatly, but 

 he did arrive alive, and he recovereci at least sufficiently to write his book 

 even though his later death would be in part due to his severe privations. 

 Nevertheless, though far from ideal, in such circumstances plankton as 

 food is most certainly worth while. 



As a commercial concern, catching plankton for food, be it for human 

 food direct or for animal feeding stuffs, is quite a different proposition. 

 Before welcoming plankton as one possible answer to the world's food 

 supply, it is first essential to look at some of the difficulties. 



Let us admit that plankton in what seems like unlimited quantities is 

 there for the taking, that its protein value is high and indeed that there is 

 the basis of a rich supply of food available to anyone who troubles to collect 

 it. The problems are in the collecting and are not so much biological as 

 engineering, and they are concerned with separating it from the sea water 

 and the salt. The often-used metaphor of a 'soup' of plankton rarely exists 

 in nature and the total volume of plankton compared with the water in 

 which it lives is extremely small. 



The first choice would be to use a plankton net or a similar filtering 

 device. This at once leads us into difficulties about mesh size. The finer the 

 mesh the more slowly it will filter the water and the more easily the meshes 



163 



