43 



expressed by several writers, being especially based on the slower 

 rate of growth of the plaice of the southern portion of the North 

 Sea, and the smaller size at which maturity is reached. The opinion 

 therefore receives strong support from a consideration of the migra- 

 tions. But the contrast between the two races is even more 

 strikingly evident when the behaviour of the mature plaice is 

 brought under review. 



Attention has alread}^ been drawn to the fact that the advent 

 of maturity impels the plaice of Northumberland and of the east 

 coast of Scotland to migrate far to the north of the school to which 

 they belong. The mature plaice of the Northumberland region 

 migrate to the Firth of Forth, to St. Andrews, even to the Moray 

 Firth ; those of the Firth of Forth region to Aberdeen and to the 

 Moray Firth ; the plaice of the Moray Firth in many cases actually 

 reach the Atlantic* The mature jol^ice of the southern race 

 migrate in the direction of the Channel, those of the Hehgoland region 

 migrating far as a rule to the west, and those of the southern 

 portion of the North Sea in many cases gaining the Channel. 



Dab. — The dabs marked on the Northumberland coast did 

 not yield a large percentage of recaptures, but these in the light of 

 the preceding statistical examination illustrate well the general 

 migrations. 



Many of the recaptures were made not long after liberation, 

 and these indicated either no migration or a shght migration to the 

 south. Three captured in October had moved from 12 to 20 miles 

 to the south, one was got in January 60 miles, and one in February 

 40 miles to the south. In June, one was caught 13 miles to the 

 south, and two, one in April and one in May, in the neighbourhood 

 of the place of liberation. The last thi'ee illustrate the return of 

 the migrants from the ^vinter migration, the first three were 

 evidently caught durmg the emigration from the Northumberland 

 region, and the January and February captures serve to indicate 

 to what a distance south and east the migrants may travel. It is 

 quite possible that these illustrate the migrations of the mature. 

 But in either case it is gratifying to obtain from marking experi- 

 ments evidence in support of the conclusions arrived at from a 

 consideration of statistics. There can be no doubt that the dabs 

 of Northumberland migrate to and from a region to the south-east. 



*!Fulton, loc. cit. 



