RAPPORTS. XIV: MASTERMAN 



— 10 



area for the plaice. One is led to the conclusion that the dabs have a habit of spring 

 and autumn movement in these inshore areas which is closely similar in its general fea- 

 tures, to that of small plaice. The curve of B 3 gives a somewhat similar result but in 

 this case the spring migration is the predominant one, whereas the autumn migration is 

 more marked in the plaice. 



The comparative 

 predominance of the 

 spring and autumn mi- 

 grations in the different 

 areas is very varied. 



Kp\ I JAN TO «1A*.Am- MfcV JWW. JUt. AUG. StP. OCT. HOV. BEC. JAN 



_l±j i I ; i i_i — i — i — i — i — i — L- 



AtcaB3 



/Vrea Bü 



Area. Cî 



rVraa. Cl 



Kfl: JAN. PEB-WR-iyH-WW juh 



jvjl. AÛ&.&ÊP. ofcrr Nov. d^cjAji 



B 



In 



all 



«Î, DJ, C>2 



and 

 the 



3> "4» 



;, an areas on 

 eastern side of the North 

 Sea, the spring migra- 

 tion is predominant 

 whereas in A T , B,, B 2 

 andC,, areas situated on 

 the western side of the 

 North Sea, the autumn 

 migration is in marked 

 predominance. 



It has been shewn 

 above that the same 

 kind of equinoctial move- 

 ments can be traced, 

 not only in the plaice 

 but in the soles, and in 

 the latter there are dis- 

 tinctions between the 

 two migrations to be 

 found in the Eastern and 

 Western sides of the 

 North Sea. 



The phenomena 

 seem to indicate that in 

 all three species there 

 are rhythmic seasonal 

 movements of an important character, having relation to the spring and autumn periods. 

 Only further biological and experimental work can hope to explain the true inwardness 

 of these movements. 

 Turbot. The curves (Figure 5 and App. Table 9) for seasonal distribution of turbot are not 



of a very pronounced character. In most areas there is a maximum for the summer 

 months, especially for June. If the curves for B 3 and B 4 be compared, they show 

 some degree of similarity, both having a second maximum in October and November 

 with minima in April and August. Area A 3 agrees in general with these two, having maxima 



Figure 5. Average catch of Turbot per day by Steam Trawlers, in certain areas 

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



