37 



The percentages of recaptures varied from 56'2 to 77*8 for the males, and from 

 24-9 to 72-3 for the females. 



EXPERIMENT I. 



25f^ November 1910. 



In this exjjeriment, 99 fishes were marked and Uberated, 37 being males, 54 

 females, and 8 whose sexes were not ascertained. The sizes of the males ranged 

 from 30'5 to 42 cm., and of the females from 29 to 58 cm. 



The numbers hberated and recaptured are shown, in groups of 5 cm., in the 

 accompanying table : — 



Of the 37 males liberated, no less than 30 were of adult size, namely, of 33 cm. 

 and over, while 7 were under that size. 



Of the 54 females, 31 were adults (38 cm. and over), while the remaining 23 were 

 under that size. 



The fish were taken at the usual place. Station VI., Firth of Forth, on the 

 afternoon of 25th November 1910, and were Uberated within an hour of their 

 capture, being in the interval kept in tanks of running water. 



The number recaptured was 67, or 67-7 per cent, of those liberated, viz. 25 males 

 (67-6 per cent, of the total males hberated), 39 females (72-2 per cent, of the total 

 females), and 3 of undistinguished sex (37-5 per cent.). 



Of the 25 males, 24 were of adult size. Their periods of Uberty ranged from 

 55 to 820 days, and averaged 293 days. Their mean size on liberation was 36-5 cm., 

 and on recapture 38-6 cm. They migrated distances of from 5 to 256 miles, the 

 average being 113 miles, and the mean rate of travel per 10 days, 3*9 miles. 



One male was under the adult size, being 31 cm. on hberation and 31-8 cm. on 

 recapture. It had moved 7 miles in 123 days, thus going at the rate of -6 mile 

 per 10 days. 



Thirty-three of the 39 females taken were 38 cm. and over on recapture, and 

 they were at liberty for from 6 to 1476 days, the mean period being 402-4 days. 

 The mean size on hberation was 39-7 cm., and on recapture 43-9 cm. They went 

 distances of from 18 to 189 miles, the average being 78 miles, and the mean rate 

 of travel per 10 days was 1-98 miles. 



The remaining 6 females were immature, the range of sizes on hberation being 

 from 29 to 34 cm., and on recapture from 29-8 to 36*8 cm., averaging respectively 

 Sri cm. and 32-6 cm. The periods of freedom varied from 29 to 326 days, the 

 mean being 151 days. The distances travelled were from 8 to 147 miles, averaging 

 42-7 miles, and the mean rate of movement was 2-8 miles per 10 days. 



The Extent and Direction of Migration. 



The first fish to be recaptured in this experiment was taken in the following 

 month, namely, on the 1st of December 1910, after a- period of 6 days. It was an 

 adult female, and was caught 27 miles to the north and east, off the Bell Rock. 

 Other 2 fish were got in this month, both females. Their movement was also 

 north-east, 1 going round Fife Ness to St. Andrews Bay, and the other to within 

 a few miles of Aberdeen. The rates of movement of these 3 fishes were respectively 

 45, 7-6, and 18-3 miles per 10 days. 



