190 



The fish used in this experiment were caught in Cruden Bay, Aberdeenshire, 

 on the 18th July, at 9 p.m., and they were Uberated on 19th July, at 2 a.m. Two 

 died in the tanks on the way. 



The number recaptured was 57, or 52-3 per cent., rather a low proportion. 

 Twenty-three (46'9 per cent.) were males, and 34 (56'7 per cent.) were females. 



Of the males, 10 were of adult size on recapture, ranging from 33-7 to 44-8 cm., 

 and averaging 38"7 cm., in comparison with a range of from 29 to 41 cm. and an 

 average of 34-4 cm. on liberation ; they were free for from 15 to 883 days, the 

 mean being 380 days ; they migrated distances of from 8 to 102 miles, the mean 

 being 393 miles, and the average rate of travel was 1 mile per 10 days. 



Thirteen of the males were under adult size, averaging 28'5 cm., and ranging 

 from 23'8 to 32 cm., compared with a range of from 23'5 to 33 cm. and an average 

 of 27"7 cm. on liberation ; they were at liberty for from 9 to 323 days, the mean 

 period being 83 days, and they moved journeys of from 6 to 55 miles, the average 

 being 26"2 miles, and the mean rate was 3' 15 miles. 



Twenty-three of the females were of adult size on recapture, ranging from 38*6 

 to 46"9 cm., and averaging 41*8 cm., as compared with a variation of from 31 to 

 47'5 cm., and an average of 38"9 cm. on Uberation ; their periods of freedom varied 

 from 13 to 701 days, the average being 275 days ; they travelled from 4 to 169 

 miles, the average being 31'1 miles, and the mean rate was I'l miles per 10 days. 



Eleven wer*^ under the adult size, the average length being 31*4 cm., and the 

 range from 25 to 37'9 cm., compared with a range of from 24'5 to 37-5 era., and a 

 mean of just .30'9 cm. on liberation ; they were free for from 10 to 209 days, the 

 average being 91'5 days, and the distances migrated were from 4 to 52 miles, the 

 average being 24'9 miles, and the mean rate of movement 2'7 miles. 



The Extent and Direction op Migration. 



First Qxiarter. — In the remainder of July, 5 of the marked fishes were recaptured, 

 2 males and 3 females, but the particulars in regard to 1 of the females were 

 not recorded. The 2 males and 1 of the females were found to the northwards 

 at distances of from 8| to 12^ miles ; the other female was got 15 miles to the south 

 and shghtly to the east. 



In August, 10 were recovered, 7 males and 3 females. Two of the females 

 and 4 of the males were taken to the south and west, at distances of from 11 to 41 

 miles, the rates of movement varying from 7' 3 to 17*8 miles per 10 days. One 

 male went to the east of the Bell Rock ; the other 3 males and the remaining 

 female were found to the westwards and slightly northwards, at distances of from 

 4 to 29 miles. 



Two males and 4 females were recaptured in September, both the males and 

 two of the females to the south and west, and 2 females to the north and west. One 

 of the males and one of the females were caught off St. Andrew's Bay, west of the 

 Bell Rock, at distances of 52 and 55 miles ; one of the females was caught to the 

 east of the Isle of May, at a distance of 51 miles ; the other niale was recaptured 

 east of the Bell Rock, at a distance of 34 miles ; the 2 females which moved to 

 the north and west were found at distances of 4 and 19 miles respectively. 



In this quarter, 21 of the marked plaice, or 36'8 per cent., were recaptured, the 

 position of capture of 20 (35" 1 per cent.) being recorded. Ten (50 per cent.) were 

 found at an average distance of 31 miles in the mean direction S. 59° W. ; 9 (45 

 per cent.), 11 A miles in the mean direction N. 73° W. ; and 1 , 15 miles S. 1° E. The 

 general feature on the chart showing the lines between the station and the place 

 of capture is the movement westwardi and south-westwards, towards the coast and 

 the mouth of the Firth of Forth. None was recaptured to the north of a hue 

 between the station and Aberdeen. With two exceptions, all the males were under 

 the adult size on recapture, while 3 females were over adult size. The repro- 

 ductive organs in all case where their condition was recorded were " immature " or 

 " very immature." 



Second Quarter. — One male and 3 females were got in October, the male and 1 

 of the females to the south and west, and 2 females to the north and west. Of the 

 2 females captured to the north and west, 1 was found at a distance of only 

 6 miles ; it measured 36'5-38*8 cm,, and was " nearly ripe •' ; the other, of 4r5- 



