PLANKTON 23 



toplankton. 155 There have been about 750 species of copepods identified, 

 averaging 2.0 to 5.0 mm. in length. The Calanus finmarchicus, for ex- 

 ample, is well recognized as an important food for many fish, and is very 

 abundant during the summer around North Atlantic shores. The colder 

 northern seas generally contain the largest quantities of copepods, though 

 the Pacific and tropical water offer more varieties. The mysids and the 

 euphasiids (krills) are the most noteworthy of the higher crustaceans; 

 they comprise some 400 species. They are much larger than the copepods, 

 the euphasiids occasionally reaching a length of 5.0 cm. As is commonly 

 the case, these larger organisms live at deeper levels and come to the sur- 

 face only during the spawning season. They are then so plentiful in Ant- 

 arctic waters that the blue and fin whales feeding on them can attain a 

 weight of sixty to seventy tons in two years. 3 G. O. Sars is cited by C. E. 

 Lu 30 as having early discovered that most fish have planktonic eggs and 

 larvae. Even herring, which lay their eggs on the ocean bed, contribute 

 to the planktonic amalgam when their larvae leave the ocean floor and 

 float to the surface. 



The use of zooplankton as a nutrient has been discussed with in- 

 creasing frequency since the latter part of the nineteenth century. 

 Although both freshwater and marine zooplankton are potential sources 

 of food, the oceanic varieties have excited greater interest. 156-158 A search 

 of the recent literature on zooplankton reveals a repetitive pattern of 

 reference to the same group of articles. One of the better summaries is 

 that of Robinson and Bajkov 159 in their 1947 survey of marine plankton 

 for the United States Army Air Force. 



W. A. Herdman 160 is frequently credited with the first publication on 

 the eating of zooplankton. His single paragraph communication to Nature 

 in 1891 related that eight yachtsmen off the coast of Norway breakfasted 

 well on cooked red copepods, probably Calanus finmarchicus ; it also men- 

 tioned that the Prince of Monaco had already considered the nutrient 

 potentialities of copepods for shipwrecked sailors. Yet even in 1888 

 Greely 161 had reported that men in his 1882 Arctic Expedition ate shrimp- 

 like crustaceans so small that 700 weighed only an ounce. In 1908, J. 

 Johnstone 162 reported Brand's chemical analysis in 1898 of dried copepod 

 plankton as follows: protein 59 per cent, carbohydrate 20 per cent, fat 

 7 per cent, chitin 4.7 per cent and ash 9.4 per cent. Shortly before the 

 first World War, Nansen 163 reemphasized the potential value of plankton 

 to castaways. In 1939, Seidenfaden 164 wrote that sailors often considered 

 prawns a delicacy. 



