SOME RESULTS OF THE INTERNATIONAL FISHERY INVESTIGATIONS. 465 



marked and liberated (according to the International methods) by the 

 Irish Fishery Branch of the Board of Agriculture and Technical In- 

 struction, and by the Lancashire and Western Sea Fisheries Committee, 

 both experiments being carried out chiefly in the Irish Sea. 



The plaice-marking experiments were designed to give information on 

 the following subjects : — 



1. The migrations of the fishes. 



2. The rate of growth of plaice in different localities. 



3. The intensity of fishing. 



An obvious objection has frequently been made to the validity of 

 results deduced from such experiments, and is this : the operation of 

 marking injures the fish, and tlie continuous attachment of a label 

 or mark to the body reduces to some extent its vitality, so that it is 

 probable that the results, whether migrations or rate of growth, 

 obtained from the marked fishes do not represent those changes under- 

 gone by unmarked fislies. The force of the conclusions depends on the 

 assumption that a marked fish behaves normally, and this is questioned. 

 The objection, which is an a priori one, probably has some force, but the 

 general opinion of those who have had experience of fish-marking 

 experiments is that the operation, if carried out carefully, has little or 

 no influence on the health or habits of the fishes dealt with. 



The migrations of the marked plaice are naturally the most interest- 

 ing of the results obtained from these experiments. In stating the 

 more prominent facts observed, one cannot, however, be too cautious. 

 Only the results of one complete year's experiments have so far been 

 tabulated and discussed, and it is most essential that these should be 

 confirmed by the further experiments that have already been made. A 

 plaice is an animal possessed both of volition and intelligence, and its 

 movements in the sea must be expected to be at times of an entirely 

 capricious nature. It is only by the study of results of extensive and 

 repeated experiments that one can hope to eliminate such accidental or 

 capricious migration results, and obtain an expression of the average 

 movements of large numbers of fishes. Bearing this in mind, we may 

 state the results at present apparent. Young plaice — that is, fishes up 

 to 8 inches in length — do not migrate to any marked extent. These 

 fish remain on the shallow-water areas immediately adjacent to the 

 places where the first year of their life has been spent. Any one who 

 observes attentively the shallow pools which have been left by the 

 receding ebb tide on almost any of the extensive sandy flats on the 

 coasts of England will be able to see numbers of small plaice and other 

 flat-fishes there during the months of June or July. At that time these 

 little fishes have just recently completed their metamorphosis from the 



