209 



to the north and west. All those fish were large, above 44 cm., on recovery, except 

 1, which measured 39-39"l cm. 



Amongst those of adult size, with " immature " ovaries (13 in number), none 

 was recaptured within the hmits of the spawning season. 



EXPERIMENT VII. 



2lst May 1913. 



One hundred plaice were marked and liberated in this experiment, 43 males and 

 57 females. The males measured from 27 to 46 cm., and 8 were under the adult 

 size (33 cm.) on liberation ; the females varied from 28-5 to 63-5 cm., and 15 were 

 under the adult size when liberated. 



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



follows : — 



cm. cm. cm. cm. cm. cm. cm. cm. 



•25-30-5 31-35-5 3G-40-5 41-45-5 46-50-5 51-55-5 56-00-5 61-65-5 Total. 



F. Lib. . 2 5 23 15 4 5 2 1 57 



F. Recap. . 1 2 16 9 4 2 — 1 35 



M. Lib. . 4 15 20 3 1 — — — 43 



M. Recap. . 1 11 15 2 1 _ — — 30 



The fi.sh used m this experiment were caught in the Dornoch Firth on the 20th 

 May, in the forenoon, and were set free, in good condition, on the following day, at 

 4.30 a.m. 



The number recaptured was 65, or 65 per cent., viz. 30 males (67-4 per cent.) 

 and 35 females (61-4 per cent.). Twenty-six of the males were of adult size on 

 recovery, ranging from 33-3 to 46 cm., and averaging 39-7 cm., as compared with a 

 range of from 29-5 to 46 cm., and an average of 36-98 cm. on Uberation ; they were 

 at Uberty for from to 945 days, the mean being 267 days, and they migrated 

 distances of from 7 to 62 miles, the mean being 26-3 miles, and the mean rate '98 

 mile. Four of the males were under the adult size, averaging 31*5 cm., as com- 

 pared with 30-25 cm. on hberation ; they were free for a mean period of 63 days, 

 and moved from 17 to 49J miles, the average being 35-7 miles, and the mean rate, per 

 10 days, 5-7 miles. Thirty-one of the females were of adult size, averaging 44-4 cm., 

 and ranging from 38 to 63-1 cm., as compared with a range of from 32-5 to 63*5 

 cm., and an average of 42-5 cm on Uberation ; they were at Uberty for from to 

 636 days, the mean being 197 days, ana they migrated distances of from 7 to 109 

 miles, the mean being 29"7 miles, and the average rate of movement I'b miles. 

 Four of the females were under adult size, the average being 33"5 cm., as compared 

 with 33-2 cm. on liberation ; they were at Uberty for an average period of 26 days, 

 and travelled from 7 to 44 miles, the mean being 29 miles, and the mean rate 10-9 

 miles. 



The Extent and Direction of Migration. 



First Quarter. — Four of the marked plaice were recaptured on the day of Ubera- 

 tion, all by a Grimsby trawler, 3 at a distance given as 8 miles to the south and west, 

 and 1 at 7 miles to the south and west ; with the exception of 1 of the females, 

 which measured 36-5-36-2 cm., they were all of adult size. 



Fourteen were got in June, 10 females and 4 males. Three of the males were 

 taken to the south and west, at distances of 28, 30, and 49| miles, the last-named 

 close to the Bell Rock, and the others in the same direction ; the other male was 

 found 11 miles to the north and east ; 7 of the females were found to the south and 

 west, at the following distances :— 21, 28, 30, 37 (to the east of the Bell Rock), 27^, 

 44 (south-east of the Bell Rock), 59 (east of St. Abb's Head) ; 1 was recaptured 19 

 miles to the north and west, and 1 at 11 miles to the north and east ; the remaining 

 female was taken ofi Noss Head, in the Moray Firth, at a distance of 109 miles to 

 the north and west, the mean rate of travel in this case being 42"8 miles per 10 

 days. 



Three males and a female were recovered in July, 2 of the males to the south 

 and west, at distances of 24 and 51 miles (to the east of the Isle of May), and the 



