SEA-FISHERIES LABORATORY. 257 



during the winter months by burrowing in the sand, 

 being shifted possibly by the disturbance of the latter due 

 to strong tidal streams during the times of the springs. 

 The medium-sized fish migrate down to the westward, 

 that is, into the warmer waters of Red Wharf Bay and 

 its vicinity : while the largest of all may migrate to 

 spawn in the neighbourhood of Bahama and the other 

 Banks eastward from the Isle of Man. This is a general 

 scheme which may be amended in detail by a close 

 analysis of all the observations to be accumulated by a 

 year or two of further work; and the deviations from 

 which may be explained by irregularities in the annual 

 cycles of physical changes in the sea. 



Experiment YI. (Chart VI.) 



We have finally to consider the results of the only 

 winter experiment made during 1913. In November 

 220 plaice were marked and liberated off Beaumaris and 

 Llandudno Bays. Fifty-seven of these fishes — that is, 

 26 % were recaptured before the end of the year. It will 

 be seen from Chart VI that most of these plaice were 

 recaught very near the place of liberation — a result which 

 has always attended the experiments made in this 

 locality. With the end of the year these recaptures 

 usually cease, the plaice having then abandoned the North 

 Wales fishing grounds. It is not quite the result which 

 we wish to attain — that of the immediate recapture of the 

 fish in the region of liberation, but the fishery in question 

 is one which may come to an end before the end of the 

 year; and the precise times at which one may carry out 

 the marking operations are dependent on other circum- 

 stances than one's own judgment as to the best times. 

 A large number of plaice must, therefore, be marked 

 and liberated before we can say with confidence what is 



