EEPORT OF THE COUNCIL, 105 



The most marked movement suggested by the position of capture 

 of the transplanted plaice was a spawning migration to the Flam- 

 borough Off Ground. As is frequently the case, a greater proportion 

 of the males than of the females appear to travel, more males than 

 females leaving the bank. 



Seventy-three per cent of the recaptures were known to be made 

 by English steam trawlers, while of the seventeen per cent which 

 were returned from the Grimsby pontoon or fish markets probably 

 the majority were recovered by the same class of vessel; only seven 

 per cent are known to have been retaken by foreign fishing vessels. 



Marking Experiments. — Among the facts brought out by examina- 

 tion of the records of the plaice-marking experiments the following 

 may be mentioned. 



The recaptures of plaice marked either on the Flamborough Off 

 Ground or among the Leman Banks were with exceedingly few ex- 

 ceptions confined to a definite tract of g9*ound which follows the main 

 direction of the English coast. Its northern boundary may be said 

 to be 54° N. lat. In the Southern Bight its eastern boundary is 

 3' E. long., and north of this it is a line trending north-west to the 

 south-western extremity of the Dogger Bank. Practically no plaice 

 were recaptured to the west of a line drawn from Flamborough Head 

 to a few miles east of Cromer. Except in the late spring or early 

 summer very little trawling takes place in this region, and this may 

 account in part for the infrequency of recoveries ; but the ground is 

 the typical rough area of the North Sea, and unsuitable for plaice. 



On the Flamborough Off and neighbouring grounds the plaice of 

 immature size are markedly stationary, seldom travelling more than 

 a few miles from the point of liberation before they are caught. The 

 mature plaice, on the other hand, travel considerable distances within 

 the above-mentioned 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 ; 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 reverse is markedly the case on the Flamborough Off 

 Ground. If spent fish are left out of consideration, the above excess 

 of mature males remains ; that of females on Flamborough Ofi' Ground 

 remains also, but is very slight. It is thus somewhat uncertain whether 

 a greater proportion of the males than of the females take part in a 

 southward spawning migration, or whether the sexes both move south- 

 wards, but the females returning earlier are caught farther to the 

 north than the males. 



