218 



EXPERIMENT I. 



Uh November 1910. 



In this experiment, the large number of 246 plaice were marked and liberated, 

 at a position 22 miles south-east of Fair Isle, 59° 20' N. ; 1° 3' W., where the depth 

 is 44 fathoms. Of the total, 109 were males, 133 females, and 4 of unknown sex. 

 The males measured from 30*5 to 40 cm., and 7 were under adult size when liber- 

 ated. The females ranged from 31-5 to 48*5 cm., and 63 were under adult size on 

 liberation. 



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

 follows : — 



The fish used in this experiment were taken by the " Goldseeker " in Aberdeen 

 Bay on the afternoon of the 3rd November, and were liberated at 9 o'clock on the 

 morning of the 4th. 



The number recaptured was 147, or 59'3 per cent., namely, 63 males (57-8 per 

 cent.), 83 females (61-7 per cent.), and 1 whose sex was not ascertained. All the 

 males were of adult size on recapture, ranging from 33-1 to 47-8 cm., and averaging 

 38*6 cm., as compared with a range of from 32-5 to 40 cm., and a mean of 36-2 cm^ 

 on liberation ; they were free for from 1 to 175 days, the mean being 281 days ; 

 they migrated distances of from 6| to 208 miles, the average being 75-6 miles, and 

 the mean rate 2-6 miles. Of the females, 60 were of adult size on recapture, 

 averaging 44-1 cm., and ranging from 38-4 to 54-5 cm., as against a range of from 

 32 to 46-5 cm., and an average of 38-8 cm. on Uberation ; they were at liberty 

 for from 28 to 1313 days, the mean being 206 days ; they travelled distances of 

 from 10 to 149 miles, the mean being 52-6 miles, and the average rate 2-5 miles. 

 Twenty-three of the females were under adult size on recapture, averaging 35-3 cm., 

 and ranging from 32-5 to 37*3 cm., as against an average of 34-6 cm., and a range 

 of from 31-5 to 36-5 cm. on liberation ; their periods of freedom varied from 1 to 

 214 days, the mean being 99 days ; they moved distances of from 6 to 137 miles, 

 the average being 62-7 miles, and the mean rate 6-4 miles. 



The Extent and Direction of Migration. 



First Quarter. — In November, 1 male ana 5 females were taken, the male at a 

 distance of 6 miles to the north and west ; 4 of the females were also taken to the 

 north and west, at distances of 6, 6, 10, and 17 miles ; the remaining female had 

 moved south and west for a distance of 24 miles. 



In December, 2 males and 5 females were taken. One of the males was recap- 

 tured at the entrance to the Moray Firth, south-east of Noss Head, 73 miles to the 

 south and west, the rate of inovement being 16-2 miles per 10 days ; the other 

 male was recaptured about 5 miles E.S.E. of Stonehaven, 147 miles to the south- 

 ward, the rate of movement being 27*7 miles per 10 days ; of the females, 1 was 

 taken by a foreign trawler in the Moray Firth, at an unspecified place, and landed 

 at Ostend ; another was recaptured to the north of the Shetlands, off Noup Head, 

 61 miles to the north and west ; the other 3 were caught to the south and west, 

 2 near Noss Head, in the Moray Firth, at distances of 75 and 79 miles respectively, 

 and the third off Rattray Head, at 100 miles distant ; the rates of movement of 

 these fish were respectively 14-1, 23-9, and 26-3 miles per 10 days. 



In January 1911 3 males and 6 females were taken. All the males were recap- 

 tured to the south and west, 1 at the entrance to the Pentland Firth, 57 miles 

 distant, 1 near Noss Head, in the Moray Firth, at a distance of 73 miles, and the 

 third off Tod Head, Kincardineshire, 153 miles to the south and west ; the rates of 

 movement in these cases were 7-4, 9-3, and 21-2 miles. Two of the females were 



