288 



EXPERIM ENT VI. 



'20th September \1912. 



In this experiment, 101 plaice were marked and li})erat('d, at a slightly difTerent 

 position, viz. 58° 5' N. ; 2° 30' W., 47 being males, 53 feniiilcs, and 1 of unknown sex. 

 The males measured from 31 to 41 cm., and 3 were under adult size when liberated ; 

 the sizes of the females ranged from 32*5 to 59 cm., and 20 were under adult size on 

 liberation. 



The numbers liberated and recaptured, arranged in 5-cm. groups, are as 

 follows : — 



The fish used were taken by the " Goldseeker " in the Dornoch Firth, some 

 hours before they were marked and liberated. 



The number recaptured was 55, or 54*4 per cent., viz. 27 males (57-4 per cent.) 

 and 28 females (52-8 per cent.). Twenty-five of the males were of adult size on 

 recapture, measuring from 34-7 to 44 cm., and averaging 37-6 cm., as compared 

 v\dth a range of from 33-5 to 41 cm. and a mean of 36-8 cm., on liberation ; they were 

 free for from 19 to 524 days, the mean being 163 days ; they migrated distances of 

 from to 88 miles, the average being 28-6 miles, and the mean rate 1-7 miles. 

 Twenty-one of the females were of adult size on recapture, averaging 43 8 cm., and 

 ranging from 39 to 59-3 cm., as against a range of from 32 -5 to 59 cm., and an average 

 of 42-4 cm. on liberation ; they were at liberty for from 20 to 507 days, the mean 

 being 160 days ; they migrated distances of from 11 to 63^ miles, the mean being 

 23*4 miles, and the average rate 1-5 miles. Seven were under adult size, averaging 

 36-2 cm., as against 35*9 cm. on hberation ; they were at liberty for a mean period 

 of 127 days, and migrated from 7 to 44 miles, the mean being 19-2 miles, and the 

 mean rate being 1 '5 miles. 



The Extent and Direction of Migration. 



First Quarter. — ^None was taken in September, but in October, 6 males and 

 5 females were recaptured ; 1 of the males was taken at the place where it was 

 Liberated, after 30 days ; 2 males were found off Noss Head by a German trawler, 

 and landed at Geestemiinde ; another male was taken 7 miles to the north and west, 

 and 1, 13| miles to the north and east, and 1, 11 miles to the north and east ; of 

 the females, 3 were found at 11, 18, and 29 miles to the north and east ; 2 females 

 were taken to the north and west, at 7 and 13 miles respectively. 



In November, 3 males and 5 females were got ; 1 male was taken 27 miles 

 to the north and west, near Noss Head, another 20 miles to the north and east, 

 south-east of Noss Head, while a third was recaptured in an unusual position, near 

 Tod Head, on the east coast, 88 miles to the southwards, having migrated at the 

 mean rate of 15-2 miles per 10 days ; of the females, 3 were taken to the north 

 and west, 2 at 14 and 1 at 28J miles, the latter close to Noss Head ; 1 was recaptured 

 14 miles to the north and east, and 1, 32 miles to the south and east, near Rattray 

 Head. 



In December, 3 males and 4 females were recaptured, the position of 1 of the 

 females not being recorded. Of the others, 2 were taken to the north and east 

 at distances of 15i and 25 miles, the fourth female being recaptured on the north 

 coast at 63 miles distant, and the 3 males at 15-|, 16, and 25 miles distant to the 

 north-east. 



In this quarter, 26 fish, or 47-3 per cent., were recaptured ; the positions were 



