64 Part III. — Tiuenty -seventh Annual Report 



lower limit is probably as low as 18 cm. By applying the generalisation 

 that the last herrings to spawn in the season ai'e probably spawning for 

 the first time, the upper limit of the first summer-spawning group would 

 be taken as 30 cm. The developing summer-spawners measured in 

 August 22 to 30 cm. in length. I think, then, that the first spawning 

 group of summer-spawners may be represented by the lengths 18 to 30 cm. 



What is the age of the herring when it spawns for the first time ? 



Attention may be directed to the immature herrings obtained in 

 February. It may be taken for granted that a fish derived from eggs 

 spawned in winter will itself spawn in winter. In the Firth of Tay, in 

 two separate samples, the immature herrings ranged from 7 to 19 cm. 

 and from 8 to 20 cm. respectively. The herrings leaving the immature 

 group are 17 to 26 cm.; but, as I have indicated above, I consider the 

 lower limit should be less than 17 cm. This group is the first summer- 

 spawning group. There is also present a group six months younger, 

 viz., a winter-spawning group. What, then, is the upper limit of 

 the v;'inter-spawning group among the immature herrings ? If the 

 matter be tested by the amount of abdominal fat present, the limits of 

 the herrings having no abdominal fat give 8-17 cm., vide p. 56. But the 

 amount of abdominal fat is not an altogether satisfactory standard. A 

 number of herrings 8 to 1 cm. in length had much abdominal fat, so that 

 the presence of abdominal fat is not necessarily associated with an 

 impending maturity. When restricted to herrings 13 cm. and over in 

 length it appears to be of value. I consider that the limits 7 to 17 cm. 

 form part of a winter-spawning group six months younger than the first 

 summer-spawning group. This winter -spawning group is, I think, one year 

 old. The herring, I am therefore of the opinion, spawns at two years of 

 age. 



The herrings obtained in December in the Tay, measuring from 5 to 

 15 cm., would be 10 or 11 months old. 



The following Table exhibits the age of certain samples, so far as I have 

 been able to determine : — 



February. — Herrings, 7-(17) cm. (2|-6| inches) long — 1 year old 

 winter-spawners. 



February. — Herrings, 17-29 cm. (6|-11§ inches) long — 2 years old 

 winter-spawners. 



February. — Herrings, 22-32 -f cm. (8|-13 inches) long — 3 years old 

 winter-spawners. 



February. — Herrings, 17-26 cm. (6| -10| inches) — 18 months old 

 summer-spawners. 



June. — Herrings, 18-28 cm. (7^-11 inches) — 22 months old — summer 

 spawners. 



The 18 months old winter-spawners (in summer) appear to be larger than 

 the summer-spawners at the same age (in winter). The latter had in their 

 short existence passed through two winters and one summer, while the 

 former have had the advantage of two summers and one winter. That 

 may account foi' the appearance of the large immature herrings in summer. 



As the spawning period is very extended on either side of the principal 

 month in both winter and svimmer, it follows that there must be a con- 

 siderable range in the size of the herrings in February. It may happen 

 that this range may be gradually reduced as the herrings grow older, since 

 the rich feeding season of spring and summer may give the backward 

 herrings the opportunity of making up some of their leeway. 



My results, then, are in agreement with those of Sim and Cunningham 

 on the question of the age at first maturity— that is, two yeai^s. The 

 smallest mature herring which I have examined was 17 cm. in total length, 

 i.e., just under 7 inches, which was given by Huxley for the smallest ripe 

 fish. 



