100 BRAIN AND BODY OF FISH 



Their diet is of herring and whiting, also hermit crabs, various other 

 crustaceans such as Norway lobster, molluscs and Aphrodite. But 

 if the stomach contents of this fish are classified according to the 

 size of the fish, it is found that those of 15 cm. have no fish in their 

 stomachs, but when the length of 30-60 cm. is reached 50 to 67 per 

 cent, of the contents consists of fish. But when we look at the 

 records for Crustacea it is found that the small fish contain Crustacea 

 up to 100 per cent. ; but as the size reaches 60 cm. the j^ercentage 

 falls to 63 per cent. The small number of polychaetes and mollusca 

 remains constant. 



The whiting, the next in our series, has a diet which might 

 appear to vary according to the observer ; but this is not really so, 

 as when one studies the sites from which the specimens were caught, 

 it will be found that stomach contents give very conflicting results. 

 Some authorities say that the food of this fish is mainly whiting and 

 herring, and shrimps in large quantities. Cunningham found that 

 in the Firth of Forth their principle food was fish and Crustacea, 

 65 per cent, of the former and 37 per cent, of the latter. On the 

 other hand, Todd, in the report of the Food of Fishes (North Sea) 

 gives Crustacea 67 per cent, and fishes 40 per cent., which is the 

 reverse of Cunningham's data. But if we analyse Todd's statistics, 

 we will find that on certain banks as the Leman Ground, that fish 

 were 91 per cent, and, if herring were about, 88 per cent. 



The ling is a voracious animal of prey, and devours all varieties 

 of cod, whiting, mackerel, megrims, dabs and haddock. All writers 

 agree that it lives almost entirely on other fish and is a nocturnal 

 feeder. 



The pollack is another voracious feeder on herring, sprats, 

 pilchards and mackerel. It is purely a fish eater. 



It has been suggested above, that the pattern of the medulla 

 in the cods shows a gradual transformation as the species changes 

 from a purely crustacean and molluscan diet to a purely fish diet. 

 When we consider the facts, just described, it would seem more 

 accurate to describe the gadoid brain as being of three types : I. — 

 With well-marked facial lobes, as exemplified by the haddock ; 

 II. — Facial lobes small, but large somatic -sensory lobes, as in the 

 cod and whiting, which are both molluscan and crustacean in their 

 diet and also fish eaters. III. — Large somatic-sensory lobes, 

 embracing very small facial lobes, as in the ling and pollack ; and 

 as we have seen, also in the turbot ; these are predacious fish, feeding 

 solely on fish. In relation to its shell-fish tastes it may be mentioned 

 that in both cod and pouting taste-buds have been described on the 

 lips, barbel, pectoral fins and the body. 



