240 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



REPORT ON THE EXPERIMENTS WITH MARKED 

 FISHES MADE DURING THE YEAR 1913. 



By Jas. Johnstone, D.Sc, and T. Monaghan. 



(With Tables and Charts.) 



The object of the experiments of 1912 and 1913 has 

 been to provide data confirmatory of the former experi- 

 ments. Plaice have been marked and liberated on the 

 same grounds, and at similar seasons during various years, 

 until a mass of results has been obtained which can be 

 summarised, all the experiments made under the same 

 conditions being grouped together. It is hoped that, 

 in this way, cumulative evidence of the regular yearly 

 migrations, free from any accidental results, may be 

 obtained. When we have such a general picture of the 

 migratory movements of plaice in the Eastern half of the 

 Irish Sea, the results of any single experiment can be 

 considered by themselves, so that the factors of migration 

 peculiar to the season in question can be considered. In 

 1910 a general summary of the experiments of earlier 

 years was made, with the object of obtaining suggestions 

 for future work. These suggestions have been applied in 

 the experiments of 1912 and 1913, and it is proposed that 

 the same general lines of work be followed in 1914. After 

 that, the deviations from the normal which may be 

 observed in individual experiments may usefully be 

 studied in relation to unusual physical or other conditions. 



Throughout the experiments of these and former 

 years the object in view has been simply that of attaining 

 a knowledge of the movements and rate of growth of plaice 

 living in the Lancashire and Western Sea Fisheries Area. 



