CHAPTER XVII 

 FOOD-MATTERS IN THE SEA 



We arrive finally at these very fundamental questions : 

 What is the manner of nutrition of all Hving organisms of 

 the oceans ? and What are the ultimate food-matters in the 

 water ? 



It will be agreed that the food of the economic animals 

 in the sea/ such as fishes, shell-fish and crustaceans, must 

 always be of interest and importance to man, and it is 

 commonly supposed that the larger marine animals feed 

 upon the smaller and simpler until organisms of microscopic 

 size are reached, which in their turn are nourished upon 

 inorganic substances dissolved in the sea-water. It has 

 frequently been pointed out that, in addition to the great 

 feeding-grounds on the sea-bottom where molluscs and 

 worms and zoophytes abound, the plankton (small floating 

 organisms of many kinds, both plants and animals) which 

 is abundant in most seas at nearly all times must be a 

 valuable constituent of the food both of young fishes of 

 various kinds and also of adult pelagic or migratory fishes 

 such as the herring and the mackerel. Of the innumerable 

 organisms in the plankton, two groups are of primary 

 importance in this connection : viz. (1) the Copepod 

 Crustacea, small animals on the average perhaps a tenth 

 of an inch in length, forming an excellent food like lobsters 

 or shrimps, and sometimes present in summer in great 

 abundance locally so as to constitute shoals upon which 

 mackerel, herring and other fishes are known to feed ; and 



312 



