SCIENTIFIC TRAWLING 181 



1909 was to ascertain the movements of plaice east of 

 the Dogger, when at a larger size than those fishes 

 which were marked in the majority of the experiments 

 carried out on the Eastern Grounds. In July 317 plaice 

 were accordingly marked in Clay Deep and the vicinity. 



It was found that with rare exceptions the recaptures 

 of plaice marked either on the Flamborough Off Ground 

 or among the Leman Banks were confined to a definite 

 tract of ground which follows the main direction of the 

 English coast. Very few recoveries took place to the 

 west of a line drawn from Flamborough Head to a few 

 miles east of Cromer. Very little trawling, however, 

 takes place in that region, except in the late spring or 

 early summer, while the ground, being the typical rough 

 area of the North Sea, is unsuitable for plaice. Of the 

 recaptures 73 per cent, were known to be made by 

 English steam-trawlers, while of the 17 per cent, which 

 were returned from the Grimsby pontoon or fish-markets 

 probably the majority were recovered by the same craft, 

 for only 7 per cent, are known to have been retaken by 

 foreign fishing-vessels. 



On the Flamborough Off and neighbouring grounds 

 the plaice of immature size are markedly stationary, 

 being mostly caught after travelling a few miles from the 

 point of liberation ; on the other hand, mature plaice 

 travel considerable distances within those limits, in what 

 is clearly a spawning migration. Spawning plaice are 

 taken on the Flamborough Off Ground and in the south 

 of the Southern Bight, and spent plaice at these and 

 intermediate positions. The number of mature, 

 spawning, or spent males taken in the Southern Bight is 

 in distinct excess over that of the females, while the 



