23 



being counted as the second winter ring, is probably two-and-a- 

 half years old, and that fish with two winter rings and spawTiing 

 in the autumn shoals are probably three years old. 



Such a variation in age for the reaching of first maturity is 

 of interest, especially for the herrings from the Shetlands and 

 Stornoway. But the feature is not without parallel amongst 

 other fish, for various wTiters have drawn attention to the age 

 when salmon and trout may reach first maturity. Some of the 

 young males may spawn before their first descent to the sea, and 

 other fish spend four or five years in the sea before ascending the 

 rivers for their first spawning. 



Growth, Table III. — In this paper the term growth is to be 

 taken as meaning the expression of the position of the winter 

 rings of the scale in terms of the length of the herring ; first year 

 gro\^'th and second year growth refer to the length of the fish as 

 calculated from the position of the first and second winter rings. 

 The growth is expressed to the nearest centimetre, 7-6 to 8-5 cm. 

 being taken as 8 cm. 



In last year's Report, page 25, it was stated that the growth 

 up to the formation of the first winter ring would vary according 

 to the period between birth and the formation of the first winter 

 ring, or, expressed in other words, there would be a difference 

 between the first year growth of j^oung fish arising from spring 

 and autumn spawners. Whilst other factors, such as potentiality 

 for growth, habitat and abundance of suitable food for the young 

 fish, will doubtless have considerable influence on this first year 

 growth, the time factor appears to be the most important. It is 

 on account of this difference of spa^\iiing times that herrings 

 have not been referred to year classes in the tables. Such a method 

 of classification has much to recommend it for herrings arising 

 from undoubted spring spawning shoals, but in British waters, 

 especially those yielding the samples here considered, we have both 

 spring and autumn sj)awners. It has not yet been proved that 

 young herrings born in the spring and autumn of the same year 

 form their first winter ring at the same time. Indeed, it is more 

 than probable that the first winter ring of herrings arising from 

 autumn spawners is not formed until the end of the following 

 3^ear. Growth after September cannot but be very slow, and it 

 is doubtful in some cases if by the end of the year the young herring 



