39 



4. — Marking Experiments. 



In the light of the foregoing conchisions from an examination 

 of the results of trawling experiments we ought to get some evidence 

 from marking experiments of such a general annual migration 

 inshore and offshore. But in seeming contradiction thereto the 

 Northumberland marking experiments disclosed an apparent 

 sedentary condition of plaice of the size of those which according 

 to statistical evidence should have migrated. The records there- 

 fore deserve a closer examination. 



Plaice. — In 1903, 470 plaice were marked between June 23rd 

 and September 9th. Two of these which were liberated in Druridge 

 Bay on September 9th were recaptured on October 1st and October 

 23rd respectively in the same area. Four marked at Blyth in July 

 were recaptured in August in Blyth Bay or about a mile to the south. 

 One was recaptured on November 5th in St. Andrew's Bay, 40 miles 

 north. The others were caught in the area of liberation, or from 

 4 to 5 miles north or south in the following IMarch to May — a few 

 in September and October of that year (1904). 



The question naturally arises therefore, why were the marked 

 plaice not captured in the Northumberland region between October 

 and March ? Only two, as has been stated, were captured in 

 October of the year of liberation, the large majority being caught 

 in the following spring. 



Fig. 6 will help us to understand the reason of the apparent 

 want of migration. The diagram shows («) the total catches of 

 white fish or line-caught fish by the fishermen in the inshore waters 

 of Northumberland from October, 1903, to September, 1904, and 

 (6) the catches of plaice during the same period. The former serves 

 to indicate that line fishing was prosecuted throughout the year, 

 and the latter the periods when plaice formed part of the catches. 

 With regard to both it is necessary to point out that line fishing 

 suffers a relapse in the summer owing to the men devoting their 

 energies to herring, and particularly to salmon fishing during that 

 season. But it will be seen that between October and March line 

 fishing was, as is the case every year, at its height. Nevertheless, 

 this is the season when plaice leave the district as is shown by the 

 curve, and this is the yearly experience as sho^\Ti by statistics and 

 by trawHng experiments. We can see the beginning of the annual 



