COUNCIL - SEPT. 1910 - APPENDIX I — 102 — 



races; the southern plaice of the North Sea, the northern plaice of the North Sea, 

 the Norwegian Sea and the Northern Kattegat, the plaice of the Southern Kattegat 

 and the Belts, the plaice of the Baltic, the plaice of Iceland and the plaice of the 

 Barentz Sea. Still further material on the difference between the southern plaice 

 and the northern plaice of the North Sea is very desirable. — The racial differences 

 are closely connected with the 



3. Age and growth of the plaice. On these points we already have 

 a very fine material. We must distinguish between slow-growing races (Baltic, 

 Barentz Sea) and quick-growing races (North Sea, Iceland). These differences are 

 of the greatest. importance for the judgment of the plaice production of the 

 different regions of the sea and for the question of overfishing. 



For example, in the less fished or almost unfished regions of Iceland and 

 the Barentz Sea we find many more old plaice than in the well fished parts of the 

 North Sea and Baltic; the accumulated stock of old fish occurring in the former 

 regions has almost quite disappeared in the latter. 



It would be very desirable, if the still unpublished age determinations of 

 plaice from all regions were made available for the General Report. 



4. Migrations of the plaice. Marking experiments. On this point 

 a very large material is unfortunately still unpublished, especially on the part of 

 England and Scotland, which nevertheless is important, indeed indispensable, for 

 the General Report. Even though we can form a good picture of the yearly 

 course of the plaice migrations in the different regions, especially in the North 

 Sea, our knowledge of the so-called spawning migrations, that is, the migrations 

 from and to the spawning grounds, leaves something still to be desired. — The 

 marking experiments are also extremely important for the estimation of the so- 

 called capture of fishing coefficient, that is, the percentage of all plaice which 

 is taken yearly by the fishery. — An important part of the marking experiments 

 is also the transplantation of plaice from one region or area to another, which 

 gives valuable information regarding the different rate of growth in the different 

 places, unfortunately the results of these transplantation experiments have only 

 been pubhshed to a very small extent. 



5. Extent of the destruction of undersized plaice. Height of 

 the size-limit. This most important part of the General Report requires above 

 all things a very large material of plaice measurements from cm. to cm. and from 

 different parts of .the North Sea, partly as data from the fish markets, partly as 

 measurements from the scientific hauls of the research-steamers. Here it is true 

 we already have a very valuable material, thanks chiefly to the English investigat- 

 ions, but it is still insufficient nevertheless, to settle certain questions regarding the 



