234 RATE OF GROWTH OP SOME SEA FISflES. 



Ads relating to Trawling for Herring on the Coasts of Scotland), 

 say that there is reason in Messrs. Yarrell and Mitchell's supposi- 

 tion that herring attain to full size and maturity in eighteen months, 

 but there is no good evidence against the supposition that it reaches 

 its spawning condition in one year. The Commissioners argue that 

 the egg of the herring is hatched in two or three weeks, and that 

 the young attain 3 inches in length in six or seven weeks after 

 hatching, and that in nine months more they would reach 10 or 11 

 inches in length. In any case eighteen months is to be regarded 

 as the maximum time required by the herring to reach maturity. 



Axel Boeck, on the other hand, the Norwegian naturalist, con- 

 cluded that mature herring were not less than three or more than 

 four years old. 



Meyer states that the spawning of spring herring in the Schlei 

 begins in March, but takes place principally in April and May. 

 At the end of May, 1874, he found in the Great Belt near 

 Schleswig many larvas 2"5 to 2*9 cm. long, on the 10th June 

 3*3 cm., and on 23rd June 4'3 cm. long. Likewise on 10th June, 

 1876, he captured larvae up to 3'8 cm. long, but the majority were 

 only 2'5 to 2*8 cm. If the longest of these came from eggs shed in 

 March they could not be more than three months old, which would 

 give an increase of 1*3 cm. per month. But the majority 2'5 to 

 2*3 cm. long observed on the 10th June could not be more than six 

 weeks old, which gives an increase of 1"7 to I'S cm. for the month. 



After about two months of age the herring changes from a trans- 

 parent elongated larva without scales, and very different in appear- 

 ance to the adult herring, to the permanent form of the adult. The 

 metamorphosed young are much deeper and thicker in proportion to 

 their length than the younger larvas. The change of form and 

 acquisition of the silvery livery takes place in the Schlei in July, 

 and by the end of that month the greater number of the spring- 

 brood have passed the intermediate stage ; they are then 4'5 to 

 5'5 cm. long. This process of change and the growth during it 

 were watched in specimens kept in captivity in a floating box, the 

 specimens grew from 2'5 to 2*8 cm. on the 11th June to 4*5 to 4"6 

 cm. on 1st August. At this length they were fully scaled. 



In July and August larger young herrings of 7 to 9 cm. long 

 (2*5 to 3" 7 inches) are found mixed with the smaller, and evidently 

 come from an earlier spawning. It is certain that the young from 

 the spring spawning, mostly 6'0 to 70 cm. in length, leave the 

 Schlei for the Baltic at the end of August and beginning of 

 September. From this time on these young fish show themselves 

 in numbers in all the bays of the Western Baltic, but mixed with 

 another generation of somewhat larger fish, from which they are 



