FISHERY RESEARCH 327 



up showing the relative frequency of the animals from 

 one spot to another. Such research has been carried out 

 in many localities and it has been found that compared 

 with other places the Dogger Bank is surprisingly rich in 

 these shellfish. The effect of this abundant supply of food 

 has been shown in a very striking manner. A large number 

 of small plaice were caught off the Dutch coast and marked. 

 Of these one half were liberated again at the spot at which 

 they were caught, but the other half were kept on board 

 the research ship in special tanks and transported up to 

 the Dogger Bank, where they were allowed to go free. 

 After a time these marked fish began to be returned by 

 the fishermen. Examination revealed the fact that those 

 that had been liberated on the Dogger Bank grew very- 

 much faster than those that had been returned to their 

 place of capture off the Dutch coast. This great growth 

 is to be correlated with the great amount of food present 

 on the Dogger grounds compared with that of those of the 

 Dutch coast. 



These results have suggested that it might be a practical 

 proposition to transplant large numbers of fish and so 

 increase the resources of the North Sea. There are un- 

 fortunately one or two obstacles in the way, such as a 

 decision as to who should bear the cost of the trans- 

 plantation, and the expense necessary for patrolling the 

 grounds immediately afterwards to prevent too eager 

 fishermen from at once fishing up all the newly arrived 

 plaice. 



One of the most instructive results of these and similar 

 marking experiments is to draw attention to the grave 

 risk that is now being incurred of depleting the stock of 

 plaice in the North Sea. Within a year of liberation over 

 a quarter of the marked fish are recaught, 250 to 300 out 

 of every 1,000 marked plaice being recaptured. This 



