SEA-FISHERIES LABORATORY. 353 



while in the North Sea immature female fish of 17 /; have 

 been observed. In the male sexual maturity is first 

 attained at a lesser size than in the female ; in Danish 

 waters ripe males 7 inches long, and in the North Sea 

 9 inches occur. The most convenient size* for purposes 

 of legislation is that lowest size at which as many Plaice 

 are mature as immature. This is the average size of first 

 maturity, and it is of course lower in the male than in the 

 female. In the northern part of the North Sea the female 

 reaches maturity for the first time on the average at 15^ 

 inches, and the male at 12^ inches. In the southern part 

 of the North Sea these sizes are 13y inches for the female 

 and 10| for the male. In the English Channel Cunning- 

 ham found that nearly all Plaice were mature at 15 inches, 

 and in the North Sea Holt found that at 17 inches nearly 

 all the fish observed were mature. In the Danish seas 

 much lower sizes than these have been estimated by 

 Petersen.! Thus the average sizes at which Plaice first 

 become mature are 10 inches in the Baltic, 11 inches in 

 the Lesser Belt and 12-13 inches in the Kattegat. In the 

 Irish Sea the smallest mature female observed was 13 

 inches in length, and the largest immature female 19 

 inches. The smallest mature male obtained was 10^ 

 inches long, and the largest immature male 13 inches. 

 Sufficient fish have not been examined in this district to 

 enable satisfactory average sizes for the first maturity to 

 be established. 



It is probable that the Plaice spawns every year after 

 sexual maturity is attained, but there is no certain 

 evidence on this point, nor is it known what are the yearly 

 increments of growth after the third year of life. In the 



* See Kyle, 18th An. Rep. Scottish Fish. Bel., Pt. iii., p. 189, 1900, for 

 a discussion of this subject. 



f 4th Report of the Danish Biol. Station, 1894, p. 3. 

 BB 



