226 



Females. — The condition of the ovaries was described in all of the females 

 recaptured. None was " spawning," " ripe," or " nearly ripe." 



Two were described as "spent" ; 1 taken in June 1911, 34 miles to the south 

 and west, east of the Orkneys, and the other in August 1912, off Aberdeen, 133 

 miles south. 



EXPERIMENT III. 



15th September 1910. 



At this station lying 19 miles E.S.E. of Fair Isle (59° 30' N.; 1° W.), where the 

 depth is aboiit 75 fathoms, 262 marked plaice were Uberated on 15th September 

 1910, viz. 100 males, 155 females, and 7 whose sexes were not ascertained. The 

 males measured from 30 to 41-5 cm., and 5 were under adult size on hbera- 

 tion ; the sizes of the females ranged from 32 to 47-5 cm., and 79 were under adult 

 size when Uberated. 



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

 follows : — 



F. Lib. . 

 F. Recap. 



M.Lib. . 

 M. Recap. 



?Lib. . 

 ? Recap. 



The fish used were taken by the " Goldseeker " in Aberdeen Bay on the 

 previous day. 



The number recaptured was 131, or 50 per cent., viz. 51 males (51 per cent.), 

 77 females (49*7 per cent.), and 3 of unknown sex (42-9 per cent.). Fifty of 

 the males were of adult size on recapture, ranging from 34-1 to 43-4 cm., and 

 averaging 38-3 cm., as compared with a range of from 32 to 41-5 cm., and a mean 

 of 36-6 cm. on Uberation ; they were free for from 1 to 954 days, the mean being 

 223 days ; they travelled distances of from 7 to 315 miles, the mean being 79-4 

 miles, and the average rate 3-5 miles. Of the females, 56 were of adult size on 

 recapture, ranging from 38*2 to 52-2 cm., and averaging 43-2 cm., as compared 

 with a range of from 34*5 to 47-5 cm., and a mean of 38-9 cm. on liberation ; 

 their periods of freedom varied from 4 to 1197 days, and averaged 339 days ; they 

 migrated distances of from 2 to 205 miles, the mean being 54-5 miles, and the 

 mean rate was 1-6 miles. Twenty-one were under adult size, averaging 36-1 cm., 

 and ranging from 32-0 to 37-9 cm., as compared with a range of from 33 to 38 cm., 

 and a mean of 35*8 cm. when liberated ; they were free from 4 to 968 days, the 

 average being 143-9 days, and they travelled from 7 to 116 miles, the average 

 being 41-6 miles, and the mean rate 3-2 miles. 



The Extent and Direction of Migration. 



First Quarter. — In the remainder of September, 2 males and 6 females were 

 recaptured, 1 of the males 25 miles to the south and east, and the other north of 

 Kinnaird Head, 75 miles to the south and west ; 2 of the females were taken at 

 9 and 38 miles to the south and west, 1, 24 miles to the south and east, 1, 10 miles 

 to the north and west, and 2 on the same day 4 miles east of Fetlar, Shetland, 

 66 miles to the north and east. These statements are according to those made 

 when the fish were returned, but some of them are obviously erroneous. Thus, 

 the male described as taken north of Kinnaird Head was captured on the day 

 following that on which it was Uberated, which would mean that it migrated 75 

 miles in a single day ! And the two females described as taken near Fetlar, had 

 only been 4 days in the water, which would mean a rate of migration of over 16*5 

 miles per day. 



Three males and 10 females were taken in October, 2 of the males to the south 

 and west, at 47 and 66 miles, the latter a little north of Kinnaird Head, and the 



