SEA-FISHERIES LABORATORY. 287 



in appraising the relative influence of sail and steam, that 

 marked fish may have been overlooked especially aboard 

 steam trawlers. On the other hand, it has to be 

 remembered that steamers are excluded from the 

 territorial waters in which the majority of the marked fish 

 were recaptured. On the whole, the figures in the table 

 agree fairly with practical experience of fishing methods 

 in the district. 



Rate of Growth of Plaice in the Irish Sea. 



This is very variable, as might be expected. The 

 growth of a fish depends on the amount of food present on 

 the ground which it inhabits, and it is well known that 

 different grounds vary greatly in this respect. The 

 present experiments were not favourable for observations 

 on the rate of growth. In order to study this to the 

 greatest advantage, a large number of fish would have to 

 be marked and liberated before the period of the year 

 when growth begins. We did, indeed, set free 566 before 

 the end of March, but of these the great majority 

 captured were taken before the end of July, and only a 

 comparatively small number after that time. In May, 

 June and July we set free 227 plaice, but few of these 

 have been recaptured. Conclusions as to the general rate 

 of growth based on these are not reliable. Up to the end 

 of July, however, our figures aiford reliable indications 

 as to the growth rate. These figures are : — 



Average increase in length up to the middle of January 0-04 inch. 



Do. do. do. February ...0-04 



Do. do. do. March 0-07 



Do. do. do. April 0-2 



Do. do. do. May 0-42 



Do. do. do. June 0-86 



Do. do. do. July 1-5 



Do. do. do. August 1-95 



Do, do, do. September. ..2-62 



