of the Fishery Board for Scotland. 



181 



The growth of the sprat is thus slow compared to most of the Gadoids, 

 but it is, of course, a much smaller species. Its growth is not greatly 

 inferior to that of the Norway Pout, the smallest of the Gadoids I have 

 dealt w r ith. 



In winter, moreover, the curves and measurements show that the 

 growth is very much slower ; most of it appears to take place between 

 April and autumn. In this respect the sprat resembles other fishes. 



There is one remarkable circumstance about the sprat, that after the 

 third or fourth generation spawns it dies or disappears. Very few fishes 

 seem to survive to the following year ; and this forms a contrast to the 

 conditions obtaining among the flat-fishes and most round fishes, in 

 which many generations survive after maturity is reached and spawn 

 in successive years. 



With regard to sexual maturity and the age at which it is attained, a 

 comparison may be made between the collections from the Cromarty 

 Firth on 1st June and that from the Dornoch on the 31st March, or two 

 months earlier — two months, moreover, in which growth is comparatively 

 rapid. The curve of the former on Plate VIII (Fig. 7) shows an apparently 

 homogeneous and symmetrical group, from 73 to 110mm., with an 

 average of 92- 9mm. As already stated, the condition of the reproductive 

 organs in this series was only partially examined, but if the smaller 

 resembled those of about 104mm. — and spawning, as we have seen, goes 

 on into July, during which a considerable amount of growth occurs — then 

 the whole group would probably spawn, and these fishes were about two 

 years of age. The great group in the March collection, ranging from 

 108mm. to 139mm., were obviously all approaching ripeness or fully 

 matured, and would all spawn in the course of the season. It is probable, 

 also, from the condition of the reproductive organs, that the next younger 

 generation, or those two years of age, would spawn also before the close 

 of the season, or at all events the males would, and in that case they 

 would come into line with the series got at Cromarty, and indicate that 

 sexual maturity is reached at two years of age. 



The average length and weight of the sprats at one, two, and three 

 years of age, according to this research, are approximately as follows : — 









Increase. 





Mm 



Grammes. 













Mm. 



Grammes. 



One year, - 



63 



1-4 







Two years, - 



93 



5-0 



30 



36 



Three years, 



120 



12-5 



27 



75 



i 



In the investigation made by Jenkins, based on the examination of the 

 ear-bones, three generations were also determined, but the average sizes 

 do not correspond. His results are as follows, the weights here inserted 

 being derived from my observations on the relation of weight to length, 

 as described on page 145. 









Increase 





Mm. 



Grammes. 













Mm. 



Grammes. 



First year, - 



75 



2-5 







Second year, 



110 



9-2 



35 



67 



Third year, - 



130 



16-4 



20 



7-2 



