100 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



REPORT 0^ MEASUREMENTS OF IRISH SEA 

 PLAICE MADE DURING THE TEAR 1909. 



By Jas. Johnstone. 



1. INTRODUCTION. 



2. THE DATA: TABLES AND GRAPHS. 



3. MODAL SIZES ON THE FISHING GROUNDS. 



4. AGE-GROUPS. 



5. LENGTH AND WEIGHT. 



6. INFLUENCE OF SIZE OF MESH. 



7. SEXUAL MATURITY. 



1. The data which are tabulated and discussed in the 

 present Report relate to the measurements of some 55,000 

 plaice made during the year 1909. This investigation 

 was begun in the summer of 1908 and was intended to 

 yield results which were to be used in connection with 

 plaice-marking experiments. It was found whenever it 

 was attempted to make a summary of the latter results, 

 that it would be most advantageous to consider the modal 

 sizes of plaice inhabiting the various plaice-grounds. 

 But it was also seen that the results of the measurements 

 of a large number of plaice and soles would afford data 

 of the greatest possible value in relation to the question 

 of the regulation of the trawl-mesh — a matter, which it 

 is needless to point out, has been the cause of much local 

 controversy. This latter object has been kept continually 

 in mind during the progress of the work. 



It might be thought that the results of the statistics 

 of fish landed at the ports would supply just the informa- 

 tion required, but unfortunately this is not the case. 

 It may be interesting to know what quantities and 

 values of fish are landed monthly at the ports, but 

 the really important questions which arise in the 

 course of such discussions are not answered by the 



