25 



the young of s]iring spawners from those of autumn spawners, 

 the same argument can be used to support the mixing of these 

 young fish. If the joung herrings shoal according to size there 

 will be a tendency for the largest of the young from spring 

 s^Dawners to join the shoals of 3'oung from autumn spawners of 

 the previous year. This tendency would arise as soon as there 

 was enough variation in growth and the shoaling instinct was in 

 force, and would continue as long as variation in growth existed 

 and was not affected by maturity. The result would be such a 

 mixing of the young fish as is evident from the first year growth 

 data. 



That size is a factor with regard to shoaling is supported 

 by the growth of fish with two winter rings found in the Stornoway 

 sample of 22nd July, the two samples from Wick, the first three 

 samples from Peterhead, the North Shields and Scarborough 

 samples. Details will be found in Table III., and are most striking 

 for growth up to the formation of the second winter ring. 



The immigration of herrings into our local shoals was shown 

 in last year's Report, and was arrived at from a consideration of 

 the first }'ear growth. It was found that herrings with a com- 

 paratively small first year growth came into the shoals during 

 the latter part of June and early July. Towards the end of July 

 and in August fish with a comparatively large first year growth 

 were more abundant, and in September the samples were marked 

 by the number of fish with a comparatively small first year growth. 

 Similar changes in other shoals apparently take place. 



From the Peterhead samples it will be seen that towards 

 the end of July there was present a number of fish with a larger 

 first j^ear growth than was found in the sample of 19th June, and 

 that by 20th August the fish with a comparatively small first 

 year growth were more abundant. The particulars are as follows 

 for fish with three winter rings.: — 



NUMBERS AT CENTIMETRES. 



Date. 6 7 8 9 10 11 12 13 14 15 16 Tolul. 



19/6/19 ... 2 11 12 21 11 10 9 6 7 — — S9 



29/7/19 ... 2 5 20 30 29 1-1 6 15 5 4 1 131 



20/8/19 ... 5 15 20 24 19 21 10 5 3 — — 122 



The two samples from Wick show a slight change, and 

 indicate the herrings with a comparatively large first year growth 

 joining the shoals in August. The particulars are as follows : — 



