D.— ZOOLOGY 



89 



existent. Mr. Ford, who has made a close study of this fishery since 1924, 

 has kindly supplied me with the figures shown in Table I. This Table 

 gives the returns of the fleet of steam drifters from Lowestoft which 

 annually visit Plymouth in the winter, together with Mr. Ford's observa- 

 tions on the composition of the catch. 



As with herring fisheries elsewhere, it will be seen that the catch, which 

 is best indicated by the average weight per steamer landing, has shown 

 marked fluctuations — the seasons 1924-25, 1927-28, and 1929-30 were 

 much above the average. These, however, are normal annual fluctuations 

 and they are due, as Mr. Ford has shown,^ to the great abundance of 

 five-year old fish : there were specially successful spawning seasons in 

 1920, 1923 and 1925. 



Table L — The Plymouth Herring Fishery, 1924/5 — 1937/8 



The significant point in this Table is, however, the marked change in the 

 composition of the catch which began in 1931-32 — that is to say in the 

 winter of the year in which the summer spawning fish larvae showed their 

 first signs of decline. Prior to 1931-32 the younger herring, not more 

 than six years old, always formed at least two-thirds of the catch. In 

 that season the younger fish were only 52 per cent, of the total and from 

 then on there has been a rapid deterioration, until to-day there are less than 

 20 per cent, of the younger and more than 80 per cent, of the older. 



' E. Ford, ' An Account of the Herring Investigations conducted at Plymouth 

 during the years from 1924 to 1933,' Journ. Marine Biol. Assoc, XIX, p. 373 



(1933)- 



* Data obtained by E. Ford. 



