386 INTERNATIONAL FISHERY INVESTIGATIONS. 



the Association feel coutident that our knowledge of a number of the 

 most essential matters, upon a proper understanding of which any 

 attempts to improve the yield of the deep sea fisheries must in future 

 be based, has already been considerably extended, and they are not 

 without hope that at no distant date practical measures founded on 

 a rational appreciation of the problems involved may be undertaken 

 with certain profit to the fishing industry. Meanwhile the Council 

 draw attention to the following pohits raised in the special memoirs, 

 which in their opinion seem worthy of particular consideration. 



II.— Fishery Investigations in the North Sea. 



Experiments made by marking fishes, more especially Plaice, with 

 numbered labels and returning them to the sea, where they have 

 subsequently l)een recaptured by fishermen, have furnished much 

 information on three important subjects — the migrations of the fishes, 

 the growth of the fishes, and the intensity of the commercial fishing in 

 the North Sea. The experiments have shown that the larger Plaice are 

 capable of very extensive migrations in a comparatively short time. 

 The extent and variety of the possible journeys may be illustrated by 

 two instances. A I'laice, 33 centimetres (13 inches) long, liberated on 

 December 12th, 1903, on the Leman Ground, in the latitude of Lincoln- 

 shire, was recovered by a Hastings trawler off Winchilsea, in the 

 English Channel, on March 23rd, 1904, having travelled a minimum 

 distance of 175 miles in a little over three months, whilst another fish, 

 marked and liberated on August 12th, 1903, off the Lincolnshire coast, 

 near Mablethorpe, was recaptured in April, 1904, eight months after- 

 wards, in St. Andrew's Bay, having travelled 210 sea miles from the 

 point of liberation. Such extensive migrations, however, appear to be 

 confined chiefly to Plaice of larger size, the smaller fishes (below 8 

 inches) being seldom found to travel long distances at a rapid rate. 

 During the summer months there seemed to be a general tendency for 

 the Plaice on the shallow-water " nurseries " off the coast of Holland to 

 move into deeper waters towards the north and west, whilst the fish 

 marked in the southern bight of the North Sea showed a disposition to 

 move in a northerly direction. In the winter (1902-3 and 1903-4), 

 on the other hand, many of the larger fish (above 9 inches) moved 

 southwards from the Leman Ground and the nortli-west coast of 

 Holland towards the southern bight of the North Sea. 



The intensity of commercial trawling in the North Sea is indicated 

 by the fact that out of 855 marked Plaice above 20 centimetres 

 (8 inches) in length liberated outside territorial limits the number 

 recaptured within twelve months yields a total of 21 per cent, whilst 



