m 



of them in 10,000 tons is astronomical; and we must multiply that 

 fantastic figure yet again by 100 to determine the number of phyto- 

 plankton that must be consumed by the euphausian supply of only 

 one among the tens of thousands of blue whales. Furthermore, the 

 euphausians (or krill, as whalers call them) are eaten by other kinds 

 of whales aud several other animals. 



The incalculable number of euphausians is • exceeded by the 

 number of copepods, which are also shrimplike but less than a 

 quarter of an inch long. These animals filter the smaller forms of 

 phytoplankton by means of special bristles that make a more effec- 

 tive strainer than any man-made net. In turn the copepods are eaten 

 by jellyfishes, by arrow worms, by the young of many species of 

 fishes, and by the adult herring and mackerel. 



Fisheries research cannot afford, then, to be parochial. It may be 

 necessary for one scientist or a group of scientists to concentrate on 

 one localized problem or on a limited area of the sea. In the long 

 run, though, we must take account of knowledge gained from the 

 length and breadth of the ocean — the flow of nutrients, the physio- 

 logy and movements of the plankton, the sources of food for 

 commercial fishes, their breeding and migrating habits, and so on. 



The rocky shores of most coasts abound with 

 seaweeds, important as a source of food 

 for creatures of the sea and important to 

 man commercially. Different varieties of 

 weed are found in different 'zones' along 

 the shore. In general, the weed found 

 highest on the shore is a bright green 

 species. Along the middle shore are 

 varieties of brown weed and the lowest, 

 sublittoral, zone contains red types of 

 weed which are not exposed to the air 

 for long periods of time. 



Ill 



