79 



Experiments at 3 Miles N.E. of Fidra Light. 

 Marked i)laice were liberated on two occasions, near Fidra Light, in the Firth of 

 Forth, near the soutli shore. The exact locahty was 3 miles to the north-east of 

 Fidra Island (Lat. 56° 6' N. ; Long. 2° 44' W.), with a depth of about 27 fathoms. 



experiment i. 

 5th December 1912. 



The first experiment was made on 5th December 1912, when 100 marked plaice, 

 com])rising 41 males, 58 females, and 1 of unknown sex were hberated. The fish 

 were trawled on the same day by the " Goldseeker," at the old " Garland " 

 Station VI., in the Firth of Forth, viz. off Pittenweem. 



When liberated, the males measured from 27-5 to 47-5 cm., and 11 were under 

 adult size (33 cm.). The sizes of the females varied from 27 to 51-5 cm., and 21 were 

 under adult size (38 cm.). 



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

 follows : — 



Of the males recaptured, 25 were of adult size, ranging from 33-9 to 43-5 cm., 

 and averaging .38-5 cm., as compared with a range of from 30 to 47-5 cm., and an 

 average of 35.9 cm. on hberation ; they were at Hberty for from 71 to 1124 days, the 

 mean being 319 days ; they migrated distances of from 11 to 271 miles, the average 

 being 97-8 miles, and the mean rate of movement 3-5 miles. Four of the males 

 were under adult size on recovery, averaging 31-5 cm., as against 31-2 cm. on 

 liberation ; they were free for an average period of 110 days, and migrated from 

 6 to 108 miles, the mean being 40 miles, and the mean rate of travel 3*6 miles. Of 

 the females, 32 were of adult size on recapture, ranging from 38-3 to 50-9 cm., and 

 averaging 43-6 cm., as compared with a range of from 31-5 to 50 cm., and a mean of 

 40-4 cm. on hberation ; they were at hberty for from 21 to 863 days, the mean 

 being 329 days ; they migrated distances of from 8 to 170 miles, the average being 

 63 miles, and the mean rate of movement 1-9 miles. Nine of the females were 

 under adult size on recapture, averaging 35-4 cm., as compared wdth 34-4 cm. on 

 hberation ; they were at liberty for an average period of 126 days, and moved dis- 

 tances of from 7 to 145 miles, the mean being 62-1 miles, and the mean rate of 

 travel 4-9 miles. 



The Extent and Direction of Migration. 



First Quarter. — Two females were recaptured in December, both in Aberdeen 

 Bay, at a distance of 72 miles to the north and east, 1 after 21 days, and the other 

 after 25 days, the rates of movement, respectively, being equal to 34*3 and 28*8 

 miles per 10 days ; both were " nearly ripe." 



One male and 2 females were taken in January 1913 ; 1 of the females was found 

 in the Firth of Forth, to tlie north-west of the station, off Largo, at a distance of 7 

 miles ; the other female was recaptured far offshore, at a distance of 67 miles 

 E.SE. from Buchanness (Lat. 57° 21' N., Long. 0° 20' E.), at a distance of 127 

 miles, the mean rate of travel being 22-3 miles per 10 days ; the male was taken to 

 the westward, at Aberdour, in the Firth of Forth, at 19 miles distant. 



Five males and 3 females were recaptured in February, all but 2 of the males 

 to the north and east. One male was got in the Firth of Forth, off Wemyss, at a 

 distance of 11 miles to the north and west ; another, 13 miles to the east and south 



