200 



EXPERIMENT V. 



2\st September 1912. 



One hundred plaice were marked and liberated in this experiment, 44 males, 

 55 females, and one of undetermined sex. The males ranged in size from 30 to 

 44 cm., and 4 were under adult size on liberation ; the females ranged from 31*5 

 to 53 cm., and 22 were under the adult size when liberated. 



The following table shows the numbers of those marked and recaptured, 

 arranged in 5-cm. groups : — 



? Lib. ... — 1 _ — _ _ 1 



The fish wliich were marked were taken by the trawl of the " Goldseeker " in 

 the Dornoch Firth, Moray Firth, in the middle of the day on 20th September, and 

 were liberated at 11 a.m. on the 2lRt. 



The number recaptured was 40, or 40 per cent., a very low proportion, viz. 

 11 males (24-4 per cent.) and 29 females (52-7 per cent.). All the males were of 

 adult size when recaptured, the sizes ranging from 34-8 to 40"5 cm., and averaging 

 37"2 cm., as compaied with a range of from 31"5 to 37 cm. and an average of 35*3 

 cm. on hberation ; they were free for from 26 to 986 days, the mean being 269 

 days ; they migrated distances of from 7 to 65 miles, the mean being 21"2 miles, 

 and the average rate of movement '8 mile. Twenty-three of the females were of 

 adult size when recaptured, ranging from 38 to 47'5 cm., and averaging 42-7 cm., 

 as compared with a range of from 32 to 46 cm. on hberation, and an average of 39"25 

 cm. ; they were at liberty for from 25 to 882 days, the mean being 308 days ; they 

 migrated for distances of from 3 to 56 miles, the av<:'rage being 18'9 miles, and the 

 mean rate of movement "6 mile. Six were under the adult size, averaging 36*1 cm., 

 as compared with 35*7 cm. on Hberation ; they were free for a mean period of 

 135 days, and travelled distances of from 6 to 51 miles, the mean being 23" 1 miles, 

 and the average rate 1*7 miles. 



The Extent and Direction of Migration. 



First Quarter. — None was taken in the remainder of September. Two males 

 and 3 females were captured in October, 1 male and 1 female at 9 and 13i miles to 

 the north and west, 1 female 4 miles to the south and cast, and a male and a female 

 to the south and west, at distances of 7| and 19 miles. Two females were recovered 

 in November, one 11 miles to the north and east, and the other off Rattray Head, 

 at a distance of 42 miles to the north and east. One male and 4 females were 

 taken in December, the male 24 miles to the south and west, a female 19 miles in 

 the same direction, and another female 43| miles in the same direction, to the east 

 of the Isle of May ; a female, of 42-42 cm., and described as " spawning," was taken 

 lOi miles to the westwards, and another, of 46-45"5 cm., and "nearly ripe," at 

 17 miles to the north and west. 



In this quarter, 12 of the marked plaice, or 30 per cent, were taken, 5 (4r7 per 

 cent.) at an average distance of 23 miles in the mean direction S. 56° W. ; 3 (25 per 

 cent.) at an average distance of 13 miles in th*^ mean direction N. 64° W. ; 2 to the 

 north and east, and 1 each to the south and east and to the west. The chart shows 

 the general lines of migration west and south-west towards the coast, from about 

 the level of Tod Head to St. Abb's Head, but 3 fishes were recapured to the north 

 of the station. 



Second Quarter.— A male and a female were recovered in January 1913, the 

 male, of 36-36"3 cm., and "ripe," near Buchanness, 35 miles to the north and west, 



