94 



January 1911, had migrated south and east for 5 and 16i miles, at the rate of 16*6 

 and 2" 7 miles. One was recaptured 12 miles to the north and west after 98 

 days, the rate being 1'2 miles, and the other had moved 5 miles south and west, 

 the rate being 2 miles. 



It is evident, from the above statement, that the majority of the adults migrated 

 to the northwards for the purpose of spawning, and sometimes with great rapidity ; 

 but several of them remained in the neighbourhood of the place of liberation. 



Relation of Movement to Size. 



As a rule, the largest males and females migrated long distances, but there were 

 exceptions, especially among the females. Of the 10 largest males, on liberation 

 or recapture, 8 iingrated northwards for distances of from 30 to 215 miles ; 

 the reproductive organs of 2 caught in October were " immature " ; in all the 

 others, they were " ripe," or " nearly ripe," or " spent," But a male, which 

 measured 35 cm. on liberation and 41*9 cm. on recapture, and which had been at 

 liberty for 754 days, was taken in December, only 4 miles to the south-west, "nearly 

 ripe." Another, of 40'5 cm., was got 13 miles to the north and west, towards 

 the coast of Fife, after 19 days ; it was " almost ripe." Of the 8 largest females, 

 4 were recaptured in the months of February and May, from 64 to 126 miles 

 distant to the northwards ; the condition of the reproductive organs of 3 was 

 ascertained, and they were "almost spawning" or "spent." Three were re- 

 captured to the south and west, distances of 13, 14, and 33 miles respectively ; 1 , 

 in December, was "almost ripe " ; 1, in June, was " immature " ; and the third, 

 in August, was not determined. The most remarkable case was the female which 

 measured 38'5 cm. on liberation and 53*1 cm. on recapture, caught in March 1915, 

 after 1566 days ; it was fomid only 11 miles to the south and east of the station, 

 and was " spent." 



experiment II. 



2lst March 1911. 



In this experiment, 51 fishes were marked and liberated, 20 being 

 males, 30 females, and i whose sex was not determined. The sizes of the 

 males ranged from 29-5 cm. to 37 cm., and the sizes of the females from 27"5 cm. 

 to 50 cm. The numbers liberated and recaptured are shown in the accompanying 

 table, in groups of 5 cm. 



The fish in this experiment were, on the whole, smaller than usual, 22 

 of the 30 females and 6 of the 14 males being under adult size when liberated. 



The fish were taken by trawl at Station VI., Firth of Forth (off St. Monans). 

 about 2.35 p.m. on the 21st March, marked and placed in tanks with a good circula- 

 tion, and liberated at 6.45 p.m. 



The number recaptured was 35 (or 68" 6 per cent, of the total marked), viz. 

 13 males (or 65 per cent, of the total males marked), and 22 females (or 

 73" 3 per cent, of those marked). The proportion recaptured in each of the 5 cm. 

 groups is indicated in the above table. Of the 13 males, 11 were of adult 

 size on recapture ; their periods of liberty ranged from 43 to 404 days, and 

 averaged 241 day^ ; their average size on liberation was 34-6 cm., and on recapture 

 38*3 cm. ; the distances migrated ranged from 4^ to 160 miles, the mean being 

 .53-7 miles, and the average rate per 10 days was 2-2 miles. The 2 immature 

 males were at liberty for 11 and 38 days respectively; 1 migrated 23, and the 

 other 5 miles. 



