92 



Percentages of Mature Female Plaice at Various Sizes. 



Immature. 



Mature. 



Percentage of 

 Mature. 



In general, female plaice were observed to be mature at 

 about 33 cms. in length and at about Age-group IV. (IV, V, 

 etc., mean over 4 years and under 5, over 5 and under 6, etc.) 



At the same time that these hauls were made a number 

 (100) of surface drift-bottles were set free, the object being to 

 ascertain in what directions the plaice eggs spawned on the 

 " Slaughter " grounds would be carried during the period when 

 they, and the larvae hatchmg out, would be pelagic in habit. 

 About half of these drifters were ultimately recovered and all 

 of them were picked up along the South Coast of Scotland. 



This is what is to be expected, because the prevailing 

 winds during the late winter and spring are from the 

 South to West in this region. There were also some East to 

 North winds, and these might have been expected to carry 

 the bottles down towards the coasts of Isle of Man and 

 Lancashire, but this was not the case. The tidal streams 

 in the Irish Sea, North of the line joining Ramsey and 

 Morecambe Bays, set in and out through the North Channel 

 (between Mull of Galloway and the Antrim coast) and then 

 North and South between Isle of Man and the Cumberland 

 coast. Further, we see that there is a gradual, resultant drift 

 of water, from the sea off the Lancashire coasts, up through 

 between Isle of Man and Cumberland and then out through 

 the North Channel. Therefore an unusual spell of North to 

 East winds might, indeed, drive the drifters down to the 



