156 



Part III. — Twenty-second Annual Report 



females obtained was 12 inches, and the smallest nearly mature 10 inches ; 

 and Holt from his observations at Grimsby placed the average limit- 

 between the mature and immature at 13 inches. 



Some observations were also made with regard to the size at which 

 maturity is reached in the plaice by the examination of the fish as landed 

 and also on board as brought to deck. In the latter case the examination 

 was only towards the close of the spawning season, when most of the 

 fishes were spent, and the information obtained in this way is therefore 

 of more limited scope. 



On the 11th and 16th February 259 were examined, of which 134 

 were females and 125 males. Among the former 50 were spawning, 

 or had the ovaries so far developed that spawning could be said to be 

 imminent. The largest immature female measured 440mm., the next 

 largest being 436mm. The smallest female found to be actually spawning 

 was 373mm., or about 14J inches, the next smallest being 382mm; the 

 smallest nearly ripe measured 360, 360, 368, and 378mm. The 

 difference, therefore, between the largest immature and the smallest 

 nearly mature was 80mm., or 3^ inches. The numbers are not very large, 

 but so far as they go they show that the average size when maturity is 

 first attained is about 43 or 44cm., that is, approximately, 17 inches, the 

 limit also found by Holt to apply to the plaice from the northerly part of 

 the North Sea, and confirmed by Kyle.* 



With the males the largest immature specimens measured 370, 367, 

 and 366mm., and the smallest spawning males measured 306, 318, and 

 330mm. ; the smallest nearly ripe was 317mm. and the next 322mm. 

 The difference in this case between the smallest mature and the largest 

 immature amounts to 64mm., or 2| inches. Probably the examination 

 of a larger number of specimens would enlarge the difference both for 

 the males and females, but as they stand they agree very well with the 

 overlapping in length of the respective series or generations. 



* Eighteenth Annual Report Fishery Board for Scotland, Part III., p. 190. 



[Table 



