COUNCIL — SEPT. 1912 - APPENDIX M — 146 — 



in a single haul over that area. 4) Determination of the so-called coefficient 

 of mortality of the plaice, which forms a maximum for the fishing coefficient. 

 The results of these extremely difficult investigations are at present subject to 

 serious errors and considerable uncertainty. It is, however, at least possible to 

 fix, with a certain degree of reliability, the size of the fishing coefficient, which is 

 here of first importance, within certain limits. This must lie between 0,20 and 

 0,40 and averages in all probability, 0,30 to 0,33. This means, that every year 

 about i/3i'<î of the number of all the plaice in the North Sea between 10 and 70 

 cm. in length are taken by the trawl, or, in other words, that the actual stock 

 of plaice in the North Sea amounts to three times the number 

 caught by the fishery. This would make the stock of plaice from abt. 12 

 cm. upwards, and over two years old, in the North Sea amount to something 

 between 1300 and 2500 million, probably 1500 milhon fish. 



Can a plaice stock of this size bear the annual removal of a third of its 

 number without lasting damage? Or in other words, is this stock of plaice being 

 overfished or not? This last question resolves itself into the query: Has 

 any overfishing appeared since the beginning of the great steam trawling fish- 

 ery; has the stock decreased, or suspiciously altered, in comparison with formerly. 

 The conclusions arrived at on this point in the General Report are as follows: 



Owing to lack of sufficient observation material, no strict proof can be shown, 

 either that overfishing has taken place and is still existing, or to the contrary. On 

 the other hand, however, everything tends to show that in all probability such over- 

 fishing does exist. We can with more or less certainty assert that the shoals of 

 plaice in the North Sea are no longer so dense as formerly, the larger and older 

 plaice are far more rare, and the average weight, length, and age of the plaice 

 have thus decreased. In order to capture a relatively equal quantity of plaice to 

 that formerly obtained, greater inroads must be made upon the stock, and this 

 affect chiefly the smaller plaice. 



A comparison of the landings of plaice from regions which have only been 

 fished by trawl at all during the last few years, e. g., the Iceland waters and the 

 Barents Sea, with those from the North Sea would seem to further indicate that 

 the North Sea, in contrast to the above named less fished waters, presents the 

 appearance of an overfished region. The plaice fishery in the North Sea presents 

 moreover a picture not only of too intensive but also of imprudent fishing, owing 

 to the useless destruction of enormous quantities of young plaice. If this be con- 



