POPULATION DYNAMICS OF THE ATLANTIC HERRING ii 



for these fisheries provide a rough measure of the total number of shots 

 made (recent, more detailed effort statistics for the Scottish fishery show that 

 on average, 'arrivals' underestimate 'shots' by about 3 per cent). 



These data show that the catch trend in the total British fishery was 

 followed in both regions; further, they demonstrate that the main trends in 

 catch were due principally to a steady fall in the size of the drift net fleets in 

 the two areas and in the effort exerted by them. This was due largely to 

 economic factors, particularly the loss of export markets for cured herring 

 and the diversion of part of the Scottish dual-purpose fleet to Danish-seining 

 for demersal species. However, a more detailed inspection of the statistics of 

 these fisheries, and of the composition of the catches, shows that other 

 important changes have taken place since the second world war, especially 

 at East Anglia. The main ingredients of these changes are described below. 



THE EAST ANGLIAN FISHERY 



This fishery, and those of other countries (principally the Netherlands and 

 Germany), in this region, is centred in October and November, on 'mature' 

 herring (principally maturity stages IV and V), on passage to their spawning 

 grounds off the Belgian and French coasts. Long-term studies of this fishery, 

 undertaken principally at the Fisheries Laboratory, Lowestoft, have shown 

 that the age composition of the exploited shoals differs between October and 

 November. In October, the grounds are occupied chiefly by the youngest 

 'recruit' age-groups (three- and four-year-olds), while in November, these 

 are replaced by the older 'adult' age-groups, mainly between five and ten 

 years of age (Hodgson, 1934, 1957; Gushing & Burd, 1957)- These two 

 components are further exploited as spawning and spent fish off the Belgian 

 and French coasts in the period November-January by the trawl fisheries of 

 continental countries (principally Germany, France, the Netherlands, 

 Belgium) which have developed since the war. After spawning they move 

 northwards from the Southern Bight and spend the spring and summer 

 feeding period in the regions to the north of the Dogger Bank (Gushing, 

 1955). They move southwards once more as adults in late summer and arrive 

 on the East Anglian grounds towards the end of October. The 'recruit' 

 component of the stock invades the East Anglian area in early October 

 from the north and east. 



The post-war changes in the size and composition of the catches in the 

 East Anglian fishery have been investigated in detail at the Fisheries Labora- 

 tory, Lowestoft, and the results are reported by Hodgson (1956, 195?), 

 Gushing & Burd (1957) and Gushing (1958, 19 59) ; therefore only a summary 

 of them is given here. 



