SEA-FISHERIES LABORATORY. 



143 



maintained till a later period of the year than in the 

 other two fishing grounds. 



I would direct particular attention to the differences 

 between the condition of the plaice from these three areas. 

 I think one can hardly regard these differences as 

 indicative of different " varieties " or " races " of plaice 

 in the way one would so interpret structural differences. 

 The grade of condition appears to depend on the amount 

 and nature of the food at the disposal of the fish on their 

 feeding grounds, and on the density of population on 

 these areas. But it is rather difficult to believe that the 

 condition depends entirely on the amount of available 



12. 



10- 



0-9- 



o-8-A 



jany.' rebf Mar ' April' May 'June July' Aug ' S>e/> ' Oct ' Nov Dec 



Fig. 20. Monthly variations in the value of the coefficient k. 



food. I examined the alimentary canals of a number of 

 plaice caught both in Barrow Channel and in Rock 

 Channel during the last two years. As a rule the plaice 

 in the former area contained small mussels from one- 

 quarter to half-an-inch in length ; while plaice from the 

 latter area usually contained small cockles, Tellina, 

 Scrobieularia, Donax, and Pectinaria, the latter animal 

 being very abundant at times. Food molluscs seemed to 

 be abundant in both areas. Nevertheless, one is forced 

 to conclude that the fish in Eock Channel are not so well 

 nourished as those in the northern area; it mav be 



