SEA-FISHERIES LABORATORY. 197 



PART III. 



The Pre- War and Post- War Plaice Fisheries. 



With the resumption of sea fishing, on the great scale, in 

 1919, the question arose : had the restrictions that were put 

 in force, as military measures, led to an increase in the pro- 

 ductivity of the sea fisheries. The question was directed chiefly 

 to the plaice because this fish had been studied more completely 

 than any other in the dozen, or so, years preceding 1914. 

 It was known that there had been a very marked falling-ofi 

 in the quantity of plaice landed from the North Sea grounds 

 during the years 1907 to 1913 — a falling-ofr which was particu- 

 larly evident in the medium-sized and larger fish ; this f alling-ofi 

 was to be traced not only in the total quantities landed, but 

 also in the quantities caught per hour's fishing. Naturally the 

 change became associated with the great expansion of steam- 

 trawling since the end of last century, and it was generally 

 believed that the plaice stock in the North Sea was a stock 

 which was being depleted by the intense fishing that had been 

 practised. 



Fluctuations in the Plaice Fishery. 



When trawling was resumed in the offshore regions of 

 the North Sea in 1919 it was seen that a considerable change 

 had occurred. The landings of plaice rose, as did the quantities 

 taken per hour's fishing. The following graphs show this 

 change very well. Fig. 15a represents the North Sea landings, 

 and it shows that the total quantity taken and brought ashore 

 by British fishing vessels fell from about 650,000 cuts, in 1907 

 to about 475,000 cwts. in 1913. Then follow several years 

 when war restrictions prevented the full exploitation of the 

 fishing grounds, and when the fishing was resumed the quantity 

 landed was found to have increased until, in L920, it exceeded 



