80 NOTES ON A FISHING VOYAGE TO THE 



Maturity Examination. 



Owing to tlie method of gutting and the recent completion of the 

 spawning season, examination of maturity was greatly facilitated. 



Before each fish was measured, the sex was determined by an 

 inspection of the reproductive organs simultaneously with an observa- 

 tion of the condition, whether immature, mature (i.e. spent), or 

 doubtful. The stage " spent " could generally be readily distinguished 

 in the females, as it was possible to press out greater or less quantities 

 of dead eggs from the ovary. Tlie characteristic flaccid appearance of 

 this organ afforded an additional criterion. 



Quite distinct were the taut, translucent ovaries of the immature 

 specimens. 



Milt still flowed freely from the majority of the males, and definitely 

 immature fish were of very rare occurrence throughout the voyage, 

 as is also the case in the spavming shoals of the North Sea. These 

 were to be distinguished by the testis appearing a mere thin band, at 

 this time contrasting with the condition of the recently spawned 

 individuals. 



However, in order that errors of observation might be avoided, a 

 special record was kept of every fish of which the condition was in 

 any way open to doubt. Into this class were placed those fish of 

 either sex which on further trial failed to show the presence of 

 sexual products, and yet seemed to differ from those which were 

 definitely immature. 



Facilities were not available, nor is the deck of a trawler an ideal 

 spot for making the minutest examinations, but it is evident that the 

 main results are not seriously affected, as the size at which the 

 maximum number of measurements of doubtful fish occurs, in the case 

 of the females, will be seen to lie in close proximity to the determined 

 average size at first maturity. In the measurements of the males, the 

 maximum lies where the size at first maturity would appear to be 

 forecasted. 



The condition of eight males* occurring in the samples was 

 remarkable from the fact that, although the fish were large, the gonads 

 were in an undeveloped condition, and I am not aware that a similar 

 feature has been recorded before. The majority of tlie lengths, viz. 40, 

 41, 47, 48, 51, 51, 53 and 57 cm., obviously render the probability of 

 immaturity very remote, and yet to judge by all appearances, these 

 fish had certainly not been in a spawning condition in this year. In 



* Two more occurred in the earliest samples, but I rejected them, thinking that the 

 apparent absence of reproductive organs was due to accidental removal in gutting. 



