Ill 



THE PONDERAL INDEX 



197 



coincide with the beginning and end of the spawning season; the 

 fish were full of spawn in December, but spent and lean in March. 

 The weight-length ratio was, of necessity, higher at the former 

 season; and the faUing-off in condition, and in bulk, which the 

 March sample indicates, is more and more pronounced in the larger 

 and therefore more heavily spawn-laden fish. 



JFMAMJJASONDJ 

 Fig. 51. Periodic annual change in the weight-length ratio of plaice. 



Periodi-c relation of weight to length in plaice of 55 cm. long 



Mean 



180 



1-08 



