SEA-FISHERIES LABORATORY. 201 



with what we otherwise know about the ground. Most 

 of the recaptures have been made in the Bay itself by 

 fishermen using " set-nets " and gill-nets, but a certain 

 number of plaice have been recaptured in the Solway 

 Firth, off the east coast of Ireland, in the Firth of Clyde, 

 and in the Irish Sea, between the Isle of Man and the coast 

 of Cumberland. The fish recaught in Luce Bay and in 

 the Solway resemble in length those about the principal 

 modal length of the whole population, that is, about 

 21 cms. Those taken in the Firth of Clyde were, on the 

 average, about 35 cms. long, those recaught on the grounds 

 between the Isle of Man and the English coast were about 

 31 cms., while two fish recaught off the east coast of Ireland 

 were 32 and 39 cms. in length. What we have to deal 

 with is, therefore, a migration of the larger fishes out 

 from the Bay in order to spawn, and a general migration 

 of the smaller fish between the Bay and the Solway Firth 

 Area. 



The frequency curve representing the lengths of the 

 plaice caught shows three distinct modes, one principal 

 mode at about 21 cms., one at 34 cms., and a less distinct 

 one at 30 cms. It is, of course, improbable that we can 

 apply Petersen's method to the interpretation of these 

 frequencies. The mode at 21 cms. may probably represent 

 the modal length of plaice of Age-Group II, the one 

 forming the greater part of the fish population, but if the 

 other modes at 30 and 34 cms. represent age-groups, we 

 should have to suppose that one is concealed by the 

 irregularities of the statistics, and is probably at about 

 length 25 cms. We have to wait, however, for a detailed 

 investigation of the. groups by means of the examination 

 of the otoliths before we can venture to assign lengths to 

 the various groups. The investigation would be a most 

 interesting one, for certain things suggest that the plaice 



