1 82 NORTH SEA FISHERS AND FIGHTERS 



reverse is markedly the case on the Flamborough Off 

 Ground. If spent fish are omitted that excess of mature 

 males remains ; so does that of females on Flamborough 

 Off Ground, but this is very slight. Accordingly, it is 

 somewhat doubtful whether a greater proportion of the 

 males than the females take part in a southward 

 migration, or whether the sexes both move southwards, 

 but the females, returning earlier, are caught farther to 

 the north than the males. Generally speaking, a greater 

 proportion of the males than the females appear to 

 travel, more males than females leaving the Flamborough 

 Off Ground. It is evident that in the Southern Grounds 

 the females move northward at an earlier date than the 

 males, the females predominating among the fish of 

 mature size marked near Smith's Knoll, off the Norfolk 

 coast, while the males are in excess in marking experi- 

 ments farther south. 



An important and interesting observation was made 

 on the fish trawled for marking, and this was that fish 

 differ as to the appearance of the eyes, which in some 

 cases are dull and in others markedly bright. In four 

 experiments the plaice with bright eyes were recaptured 

 in far greater proportion than the rest, so that it appears 

 as if the eyes afford a test of the condition of the fish. 

 The high proportion captured in the case of the bright- 

 eyed plaice was fully maintained in two other cases in 

 which only fish of that kind were marked. 



Vitality experiments were made on the plaice from 

 about fifty hauls of the commercial trawl of the Hiixley. 

 In some of these experiments a number of fish were 

 placed in the tanks immediately after capture, others 

 after an hour's exposure on deck, a proceeding which 



