INTRODUCTION TO THE FISHES 203 



have been obtained are of far-reaching importance, and deserve to 

 be far more widely known. 



I suppose most people would consider that the chances of ever 

 recovering from the sea a fish that had been marked with a label 

 and liberated would be exceedingly remote ; yet Professor Gar- 

 stang's report on his experiments on marking and liberating 

 plaice shows most conclusively that this is no longer the case 

 in the North Sea. The intensity of commercial trawling in the 

 North Sea to-day is demonstrated by the fact that out of 855 

 marked plaice liberated outside territorial limits the number 

 recaptured within twelve months yielded a total of 21 per cent. : 

 while experiments on the Dogger Bank in the spring of 1904 re- 

 sulted in the recapture of more than 40 per cent, of marked plaice 

 exceeding 10 inches in length, in less than twelve months. These 

 figures clearly demonstrate that the total annual catch of the 

 fishermen no longer forms an insignificant proportion of the total 

 stock of plaice living on the Dogger Bank. 



These experiments also yielded very interesting evidence of the 

 extensive migrations which the larger-sized plaice are capable of 

 making in a comparatively short time. In one instance a marked 

 plaice, 13 inches long, liberated on December I2th, 1903, on the 

 Leman Ground in the latitude of Lincolnshire, was recovered by 

 a Hastings trawler off Winchelsea, in the English Channel, on 

 March 23rd, 1904, the fish having travelled a minimum distance 

 of 175 miles in a little over three months. Another plaice, marked 

 and liberated on August I2th, 1903, off the Lincolnshire coast near 

 Mablethorpe, was recaptured in April, 1904, in St. Andrew's Bay, 

 having in eight months travelled a distance of 210 sea miles from 

 the point of its liberation. 



Another experiment, carried out by Professor Garstang in 

 connection with the Marine Biological Association's work in the 

 North Sea fishery investigations, revealed the remarkably rapid 

 advance in size and weight of young fish when transported to 

 favourable feeding grounds. In this experiment a large number 

 of young plaice were captured in the inshore waters which they 

 frequent in their early stages and were carefully marked, and a 

 given member at once liberated, while the rest were trans- 

 ported to the Dogger Bank, where young, small plaice are not 

 found, and liberated, a previous examination of the bottom having 



