113 



The fish used in this experinieiiL were caught at Station VI., Firth of Forth 

 (Fkike Hole), on the 6th of March ; they were marked between 5.50 and 6.50 p.m., 

 kept in tanks of running water and hberated on the 7th at 10 a.m. None of them 

 died in the tanks. 



The number recaptured was 73 (or 73 per cent, of the total marked), viz. 

 13 males (59-1 per cent.) and 60 females (76-9 per cent.). Of the 13 males, 12 

 were of adult size on recapture ; the lengths on liberation varied from 32-5 to 

 48-5 cm., the mean being 36-4 cm., and on recapture from 33*9 to 48-5 cm., the 

 average being 389 cm. ; the periods of liberty ranged from 6 to 772 days, the 

 mean being 210 days ; the distances migrated v/ere from 1 to 114 miles, averaging 

 30 miles, and the mean rate of travel was 1*4 miles per 10 days. Of the 60 females, 

 43 were of adult size on recapture ; the sizes on liberation were from 335 to 60 cm., 

 the mean being 39-8 cm., and the sizes on recapture varied from 38 to 61-6 cm., 

 the average being 42-8 cm. ; the periods of freedom were from 5 to 801 days, and 

 averaged 238 days ; the distances migrated ranged from 5 to 173 miles, the mean 

 being 31-6 miles, and the average rate 1-3 miles. Seventeen of the females were 

 under adult size on recapture ; on Uberation, the sizes varied from 31 to 38 cm., 

 the mean being 341 cm. ; and on recapture, from 313 to 37"7 cm., with an average 

 of 34r7 cm., the periods of freedom were from 1 to 120 days, averaging 31 days, 

 and the distances migrated ranged from 4 to 23 miles, the mean being 12-1 miles 

 and the mean rate 3-9 miles per 10 days. 



The Extent and Direction of Migration. 



First Quarter. — In the remainder of the month of March, 13 fishes (17-8 per 

 cent.) were recaptured, 3 males and 10 females. All had moved in a more or 

 less westward direction. Six were taken to the south and west, at distances of 

 from 5 to 16 miles, and 7 to the north and west, at distances of from 10 to 23 miles. 

 One of the females, measuring 33-5 cm. to 33*8 cm., had moved back to near the 

 position in the Firth of Forth where it was originally caught, or 23 miles in 16 days, 

 or at the rate of 14-4 miles per 10 days. All the fish, indeed, had travelled more 

 quickly than usual, and for a somewhat greater distance. In those caught to 

 the south and w^est, the average distance was 10"3 miles in an average period of 

 4-7 days, the mean rate being 2'2 miles per day. One female was recaptured 

 16 miles to the south-west on the following day, and another 3 miles almost in 

 the same direction 2 days after hberation, the rate in these cases being respectively 

 16 miles and 1-5 miles per day. With 2 exceptions, these fish, both females and 

 males, were under adult size, the 2 females referred to measuring 34 and 33-5 cm. 

 respectively. A female of 38 cm. had moved 6 miles in 7 days, and a male of 

 37-5 cm. 5 miles in 8 days. Of the 7 found to the north-west, 6 of which were 

 females, the average distance was 13-3 miles in a mean period of 7'6 days, the 

 mean rate being 1-75 miles per day. One female was adult, measuring 41 cm., 

 and the male measured 33-5 cm. With 1 exception, the reproductive organs of 

 the 13 fishes were "immature." The female, which measured 41 cm. and had 

 moved 10 miles to the north and west, was captured after 5 days, and was " half 

 ripe.'' 



lii April, 11 were recaptured (or 15-1 per cent, of the total), 10 females and 

 1 male. Particulars were obtained for all but 1 of the females. Five were 

 caught to the south-west, at distances of from 4 to 16 miles, the average distance 

 being 7*8 miles, and the mean rate 2 miles per 10 days. One was taken to the north 

 and west, at a distance of 20 miles, the rate of travel being 3-7 miles ; 1 was 

 got 9 miles to the south-east ; and 3 to the north-east, at distances of 34, 79, 

 and 86 miles, the first off Tod Head and the other 2 at a considerable distance 

 offshore from Buchanness, the mean rate of movement of these 2 being respec- 

 tively 193 and 22 miles per 10 days. The reproductive organs in all cases were 

 "immature." 



The number recaptured in May was 13 (or 18*3 per cent.), 12 being females 

 (20-7 per cent.), and 1 male (7-7 per cent.). Six, all females, had moved 

 south and west, 5 of them for 5 miles and 1 for 6 miles, after from 63 to 82 

 days (average 76 days), and the rate of movement varied from "6 to -8 mile per 

 10 days, the mean being -7 mile. Three females were found to the north-west, in 



