COUNCIL — APRIL 1912 — APPENDIX G — 120 — 



The coefficient of mortality appears to vary greatly for the different years of life, 

 being especially high for instance, in the 5 th and 6 th years. 



A fourth very important point of the plaice question is, whether the stock 

 of plaice in the North Sea is being overfished or not. If the fishing-coefficient be 

 considered as 30°/o, the question then arises, whether the yearly removal of such a 

 fraction of the stock by fishing is fully compensated by the natural power of reproduction 

 of the sea or not; in the latter case there is overfishing, in the former not. Is 

 there any means of discovering by sure signs, that the stock of plaice in the North 

 Sea is being overfished? This question must be thoroughly dealt with in the 

 General Report. It appears that a comparison of the composition of catches of 

 plaice landed from the more virgin grounds, which have only been fished for a 

 short time, as for instance the Iceland grounds and those of Barentz Sea, with the 

 catches from grounds in the North Sea, can give some explanation here. The 

 determinations of age made by me with the Iceland and Barentz Sea plaice, and 

 the series of measurements given of these plaice render it very probable that the 

 coefficient of mortality of these still less fished grounds is lower than that of the 

 North Sea, and thus also, in all probability, the fishing-coefficient will be lower. 



These are then four of the most important questions, taken as examples, 

 which the General Report has to deal with thoroughly, in order to effect which 

 it will be necessary to extract from the material to hand everything which can 

 with safety be turned to account. 



The necessity of dealing with the Report in this manner explains its 

 diffficulties, and its great extent. One word more as regards the division of the 

 General Report. 



The Report had to be prefaced by a General Introduction (p. 1 — 15) in 

 which the essentials of the plaice question and the question of protective legislation 

 were shortly explained. This introduction closes with a statement of the 8 chief 

 divisions of the Report. Part I (p. 16—64 and 15—60 resp.) gives first an 

 indispensable view of the General distribution of the plaice in the North Sea, and 

 that part of its biology which is immediately connected therewith. Then a discussion 

 of the scientific methods of research as regards the distribution of plaice in general, 

 as well as for discovering and correctly stating the numbers caught and the numbers 

 brought to land. A to some extent mathematical explanation of the division was 

 indispensable: it is chiefly based on the German investigations made by Eucken. 

 Part II is the most important and the most extensive part of the Report. It deals 

 with the size and composition of the catches of plaice landed and the stock of plaice 

 in the North Sea. The largest and by far the most important portion of this 



