280 



been said to prefer boiled potatoes to every other descrip- 

 tion of food. 



For the purpose of illustrating upon what marine fishes 

 subsist, I have deemed it advisable to select classes which 

 are most useful to man. The sea fisheries for practical 

 investigations may have their finny inhabitants (as already 

 remarked) divided into: (i) such as generally reside in 

 or near the surface of the sea ; (2) such as swim in 

 moderate depths or at the bottom, and (3) lastly, those 

 which are ground feeders. It is evident that unless the 

 food which all subsist upon is identical, and that such is 

 found at all the various depths which these different fishes 

 inhabit, what causes would be injurious to the food 

 partaken by one class may be perfectly innocuous to 

 that which the other classes live upon. The whelk, 

 Buccinum, and the mussel, Mytilus, at the bottom may be 

 consumed by bottom feeders, but they would not afford 

 sustenance to herrings which mostly frequent the 

 upper strata of our seas, where they prey upon small 

 Crustacea and other forms of food. The ground feeder, as 

 the sole, turbot, or brill live on what is normally present at 

 places they frequent ; anything which tends to injure the 

 various kinds of animal life found at these places must 

 tend to destroy what would be food for fishes. 



The heads for a brief investigation may be divided into 

 what is the food of the more gregarious kinds of fish, as of 

 the mackerel, herring, or pilchard, forms which when investi- 

 gating the subject of their food ought to be kept essentially 

 distinct from the more sedentary and local residents. And 

 in tracing this question of food it will be best to proceed 

 from the more predaceous to the more preyed upon fishes. 

 Sharks and their allies follow shoals of the herring family, 

 as I had the opportunity of investigating off the western 



