— 21 - LATER STAGES: I'LEURONECTJDS 



PART 11. 



RECOMMENDATIONS AND SUGGESTIONS. 



Perhaps the most forcible impression left by going over the publications of the year 

 1909 is the enormous amount of research which is being concentrated upon the plaice to 

 the almost entire neglect of the other species of flat-fish. 



Important results are now being discovered in all directions by different workers 

 upon different material and by different methods which, when compared and woven 

 together, as has been here attempted for the determination of spawning areas of the 

 plaice, are gradually giving a true picture of natural phenomena, — but this applies prac- 

 tically to the plaice alone. 



Yet the sole, turbot, brill and halibut, to mention no others, are of the utmost im- 

 portance. Furthermore, the questions arising out of these species cannot be separated 

 from the plaice problem. One consideration alone may be urged in illustraiion of this 

 point. The general statistics, as treated last year, indicate that the nurseries of the plaice 

 extend largely over the same areas as those of the sole, turbot, and brill. In consider- 

 ing the possible effect of excluding trawlers, either directly or indirectly, from these 

 grounds, one can hardly ignore these important and high-priced species. They afïect the 

 problem in many ways. Their presence may prevent trawlers from forsaking the nurseries 

 even when small plaice is unsaleable through restrictive measures, or their abundance may 

 be affected directly by immunity from the trawl, or by increase, in the case of the turbot 

 and brill, of their fish food — or even adversely by increased competition for food, in 

 so far as the diet is similar. Again, the sole forms the keynote to the question of regu- 

 lation of mesh, which may become of a pressing nature. 



It may be added that these species have, like the plaice, a restricted distribution in 

 the most intensely fished part of the North Sea. 



These few considerations are sufficient to indicate the need for extended study of 

 these species of flat fish. In the case of the halibut, the destruction of immature fish in 

 Icelandic waters is likely to become a question of economic importance, demanding for its 

 solution more knowledge of the species in question. 



(1) In the preceding report a "systematic investigation upon the earliest age groups 

 of the flat fish, with regard to number and sizes, in the shallow littoral waters of the 

 North Sea" was recommended for the consideration of the countries concerned and this 

 recommendation should be endorsed in the light of subsequent research. 



It is known that the littoral shores in the summer and autumn abound in small plaice, 

 turbot, brill, sole and dab, which have arrived there at the end of their pelagic drift from 

 the spawning grounds. 



It is important to determine the relative prevalence in each of the earlier years of 

 their life and the rate of growth and growth movement of each species. 



(2) The correlation of different work upon the spawning grounds of the plaice shows 

 not only the points of agreement in results but also clearly indicates the déficiences of 



