188 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



estuaries, and they are preparing to adopt a semi- hibernate 

 habit for the remainder of the winter months. (" Winter " in 

 the sea means the months January, February, and March.) 

 (2) In addition to the retrograde movement there are, however, 

 two others. Some plaice are migrating up to the N.W. towards 

 the extensive, late winter, fishing area, between Ramsey Bay, 

 in Isle of Man, and the entrance to the Solway Firth, while 

 others are migrating to the S.W. towards the " back-end " 

 plaice fishing region, just off the coasts of Anglesey and 

 Carnarvon (Red Wharf, Beaumaris, and Conway Bay regions). 

 The S.W. migration begins in September and October and 

 culminates in December, while the N.W. movement begins in 

 November and December and culminates in February. Here, 

 then, we have a continued offshore migration in direct contrast 

 to the retrograde one mentioned above. To elucidate it further 

 we must now look into the sizes of the recaptured, marked 

 plaice. Fig. 14 shows that the prevalent lengths (shortest 

 half-ranges) of the latter were : — 

 22-5 to 25 cms. on the offshore region in August. 

 22 to 25-5 cms. on the inshore region in October to December.^ 

 23-5 to 26-5 cms. on the N. Welsh region in November-December. 

 25-5 to 29 cms. on the Manx region in January-February. 

 27 to 30 cms. outside the Irish Sea in the following year. 



This latter point is one to which we return later. A 

 certain number of the larger plaice leave the Irish Sea altogether 

 and do not return. They are recaught in St. George's Channel 

 and elsewhere. 

 Further Recaptures. 



So far we have only considered the recaptures reported 

 during the months July to February, immediately following 

 the months of liberation — that is, the eight months or so after 

 the times of the experiments. Further, we have combined 

 the results of experiments made in different years — a deliberate 

 policy, When we take the various experiments separately we 



