6 



the war years on several occasions by the presence of oil on the 

 surface of the sea and on the rocks and beach. The oil caused 

 the death of many sea birds, and if at such a time the surface 

 waters are occupied by pelagic eggs and larvae of fishes, and 

 by the planktonic stages of the food of the fishes the effect may 

 be of serious importance. Our experiments go to show that 

 while the hydrographical conditions of the spawning season 

 have an influence on the success of the spawning and therefore 

 on the abundance of the year group concerned the absence of 

 food and the stunted growth are traceable to such accidents 

 as the spreading of oil over the sea at all events in territorial 

 waters. The effects are fortunately local and transient. 



In reviewing the experiments of 1920, and comparing them 

 with pre-war years it was found necessary to present a general 

 report on the results of the Northumberland Trawling Experi- 

 ments. The results bring out important facts relating to the 

 distribution and migrations of fishes and the relationships of 

 these to the currents of the North Sea. 



Mr. Storrow has contributed an account of his work on herrings 

 during the year. He draws attention again to the important 

 fact that herrings in their fourth year form the most important 

 constituent of the summer fishery along the east coast of Britain. 

 It is obvious therefore that the fluctuations in this important 

 fishery depend largely upon the success of the spawning and 

 the rearing of the season four years before that of fishing 



The samples from the Autumn shoals of 1920 showed that 

 fish with six and seven winter rings were comparatively 

 abundant and the scarcity of herrings with five winter rings 

 was a marked feature of the shoals sampled. The same year 

 classes occurred in the samples from shoals of spring herrings 

 in 1921, and their abundance and scarcity were practically the 

 same as was found in the Autumn shoals. 



The data with regard to the maturity of the shoals which 

 give the East Anglian herring harvest point to the shoals being 

 composed of full fish which assemble previous to a migration 

 for spawning in the spring. From the age composition and 

 the growth data, it is concluded that some of these herrings 

 return again to the same locality as spents and give rise to the 

 Yarmouth fishery for spring herrings. 



