NORTH SEA FISHERIES 33 



we find that in every part the North Sea 

 is peculiarly favourable for fish life. In 

 every small bay on the coast the water 

 literally teems with small crustaceans and 

 other minute living creatures : these sup- 

 ply the means of existence to other small 

 fish, and as they in their turn are swallowed 

 up by larger fish, w r e.see that plankton is 

 the base of marine life. Where there is no 

 plankton we find no fish ; when there is 

 abundance of plankton the fish are found 

 in greatest numbers. The millions of 

 herrings which annually move down our 

 coast are migrating with two objects inti- 

 mately connected, to spawn and to find 

 food in the form of plankton. 



To recapitulate : the causes which have 

 made the North Sea an extraordinarily 

 valuable and fertile fishing ground are 

 its extreme shallowness, the average depth 

 being 60 fathoms (which is only one- 

 thirtieth of that oi the Atlantic), and 

 its consequent abundance of vegetable 

 plankton owing to sunlight and the action 

 of waves reaching the sea bottom.: its 

 position favourable to a great influx of 

 currents laden with plankton ; its low 





