ÖFVERSIGT AF K. VETENSK.-AKAl). FÖRHANDLINGAR 1894, N:0 10. 587 



earlier inature. At Anholt I saw raale turbots with flowing 

 milk although they only measured 29-t-oO cm., and a male 

 specimen of 23 cm. seenied nearly mature. In the Sound they 

 seem to be still earlier developed and I saw there females of 

 29 and 34 cm. length that were perfectly mature. The sole 

 is mature at a length of 30 cm. (or less?) as even the female 

 at that size has the ovaries fully developed. 



As the couditions of life in the sea are about the same 

 for all individuals of the same fishspecies, there is at least a 

 probability that fish of the same age are about of the same 

 size. I therefore measured a good raany flatfishes and, by 

 tabulating my results, I tried, if possible, to find out the size 

 at different ages and from that the average growth per annum.^) 

 Measuring brills T fonnd more specimens grouping themselves 

 round the sizes 32, 37, 44, 50 and 55 cm. than round the 

 others. It is possible then, that these numbers represent the 

 size of different consecutive ages. The growth per annum would 

 thus be 5 — 7 cm. From the size of 32 back to 25 n^.eans 

 probably one year, and thus by deduction the age of a 25 

 cm. brill might be estimated at about 4 years. The brills 

 would then be mature at an age of 5 years. For the turbot, 

 these figures are not so easily obtained. The age-groups can 

 not be seen so plainly. It may be possible liowever that a 

 length of 33 cm. represents one group, 36 — 37 — 38 represent 

 than probably the next, 41 the foUowing and so on. The 

 average growth per annum would, if such were the case, be 3 

 or 4 cm. This is not much, but as the turbot is broader and 

 thicker, it is certainly as much increase in size and weight as 

 in the brill. Ou the other hand the turbot becomes mature at 

 a smaller size, as has been already mentioned. The table 

 giving the measurements for the sole does not so evidently 

 show the age-groups either. I obtained however more measuring 

 about 28, 32, 35, 37, 40—42 and 46 than of the sizes between. 



') C. J. Petersen was the first to achieve this with good results on other kind.-i 

 of fish (Zoarces etc). For freshwater fish the system cannot he used. 



