SEA-FlSllEttlES LABORATORY. 293 



highest percentage recovered was 25, and in three of the 

 experiments no fish whatever have been sent back. 



2. The average percentage of marked plaice 

 returned from all the experiments is 23'2. This may be 

 regarded as indicating the extent to which fishing goes 

 on on the East side of the Irish Sea. It suggests 

 about 25 per cent, of the plaice present on the fishing 

 grounds at any time will be caught by fishermen before 

 the expiry of one complete year. 



3. The majority of the fish returned have been 

 recaught by smacks. But it must be remembered that it 

 is more likely that marked fishes would escape recognition 

 if taken by a steam trawler. 



4. The increase in size of the fishes recaught agrees 

 well with previous estimates. Roughly speaking, this 

 may be put down at three inches in the year ; that is, for 

 plaice between eight and 15 inches in length. This 

 increase in growth takes place almost exclusively during 

 the months May to September. During the other months 

 of the year plaice do not grow at all. 



The increase in weight is, of course, much more rapid 

 than that in length. The weight of plaice of eight inches 

 in length varies from 75 to 90 grams (from three to four 

 ounces), while that of a plaice 11 to 11| inches long may 

 vary from 240 to 280 grams (9^ to 11^- ounces). That is, 

 a plaice which in April is only one quarter of a pound in 

 weight will, if allowed to remain in the sea, attain a 

 weight of from one-half to three-quarters of a pound by 

 the end of the following September. Marked plaice shew 

 much the same relationships of weight and length as 

 unmarked fishes. 



5. Migration paths can, so far, only be roughly 

 determined, and many more experiments will have to be 

 made before the main facts of fish migration can be 



