LATER STAGES: PLEURONECTIDS 



or no seaonal changes of any importance but the "medium" and to a greater degree, 

 the "large", show a summer maximum and a winter minimum, of considerable regularity. 

 The maximum is in June in C, D, and D, and in August in B t . 



So far as the curve of total quantities is concerned C 2 and B 5 also show a steady 

 summer rise. In the former, the maximum is in August but in the latter it is masked 

 by the autumn move- 

 ment of young plaice, 

 forming a later maxi- 

 mum in October. 



C 3 has characters 

 peculiar to itself. The 

 general curve is the re- 

 verse of the others, 

 showing a winter maxi- 

 mum and summer mi- 

 nimum. There is a very 

 slight tendency to a sec- 

 ondary maximum in 

 August, reflecting that 

 of the contiguous area 

 (B 3 ) but more confined 

 to the large and me- 

 dium. 



This winter maxi- 

 mum corresponds very 

 nearly with the dura- 

 tion of the spawning 

 season in this area and 

 probably reflects the 

 concentration due to a 

 spawning migration. It 

 is reflected in the great- 

 est degree by the "large" 

 plaice, in somewhat less 

 degree by the "small" 

 and least of all by the 

 "medium". It has been 

 found that in this area 



during the spawning season there is a large aggregation of males, which are in excess of the 

 females ; possibly this feature may explain the exceptional character of the curve for smallpsh. 



In the two inshore areas, A 3 and B 4 , the curves for dabs (Figure 4. and App. Table 

 8) have a general character with summer maxima. The winter catch is about 10 kilos, 

 and the summer about 25 kilos. 



The curves also show two maxima at April and October with a marked fall in mid- 

 summer. In this respect they have an instructive similarity to the curves for the same 



Figure 4. Average catch of Dabs par day by Steam Trawlers, in certain areas 

 of the North Sea (Mean of the 4 years 1906— 1909). 



Dabs. 



