128 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



plentiful in Red Wharf Bay. These changes arc, no 

 doubt, to be associated with variations in the hydro- 

 graphic conditions of the sea in these regions, but just 

 what is the nature of these associations is as yet doubtful. 



Fairly large catches of plaice were made in the 

 Beaumaris and Red Wharf Bay area by Captain Wignall 

 during the autumn of 1909, and the figures appear to me 

 to be very reliable and to give us a very accurate picture 

 of the distribution of sizes on this fishing ground. I 

 have grouped together all the catches made in " Beau- 

 maris Bay," " Conway Bay," " Off Orme's Head," and 

 in " Colwyn Bay." All these grounds may be regarded, 

 during this last fishing season at least, as constituting 

 practically the same area. The catches made in Bed 

 Wharf Bay have, however, been kept separate from the 

 rest, though it would not have made much difference to 

 the results had they been incorporated with the rest. 



It will be seen from the tables and from the curves 

 in fig. 12 that the plaice taken were smallest in June 

 and July, and that they become larger as the end of the 

 year approaches. The curves are uni-modal in Tune and 

 July, the mode being about 20 cms. After August the 

 dispersion increases and the fish become, on the whole, 

 larger. From September to the end of the year the 

 curves are bi-modal. Those for November are remarkably 

 similar, and the October and November curves can be 

 superposed, so alike are they in magnitude and phase. 

 This similarity appears to me to indicate that we are 

 dealing here with samples which are of great reliability. 

 In December the modal sizes are greater than in the 

 preceding months. The double mode indicates the 

 presence of plaice of Age-Groups II and III, though, of 

 course, the positions of the modes are not exactly those of 

 the maximal sizes in those groups. Plaice up to six years 



