— 21 — 



make up 25 to 70 "/o, the very large fish 5 to 15 Vo. Very small plaice under 18 cm. 

 are, according to the scientific catches, practically never caught now in this zone; only 

 in C 1 can a few now and then appear in the trawl. The question of protective 

 measures is no longer of any importance for this zone. 



Within each of the three plaice zones of the North Sea the various subdivisions, 

 the areas themselves, again show points of difference, the size of the plaice and the 

 percentage of the different size-classes being dependent on the depth of the region and 

 its distance from the coast. 



b. The English landings for the various months from the whole 



of the North Sea. 



Investigation shows, that the size and composition of the landings vary not 

 only according to the areas of the North Sea, but also, though in lesser degree, accor- 

 ding to the months. And these monthly variations are found both within one and the 

 same area, and for the North Sea as a whole. These variations are partly accounted 

 for by the fact, that the intensity of the fishery and its extent over the different areas 

 are not the same in all months (seasons), and partly due to the fact that the distribution, 

 density, and composition of the shoals on the ground are not always and everywhere 

 the same, but vary, as a result of the complicated movements of the plaice population 

 in the North Sea, according to month and season. Thus the English fishery for 

 instance, finds its greatest yield in Areas A:i, B4 and B3, in the Southern North Sea, 

 in early Summer, during June and July: in the northern areas on the other hand, in late 

 summer and early autumn, during August and September. On the other hand, while in 

 all other areas the winter catches, i. e., those of January and February, are the smallest, 

 and the catches made in summer the largest, the reverse is the case in Area C3. By 

 far the greatest yield of plaice occurs here in January and February, which is in all 

 probability due to the fact that in this area and a part of B3 lies one of the principal 

 spawning places, where great numbers of spawning fish collect in the spawning months 

 of January and February. In the composition of the catches we find, and this, 

 moreover, chiefly in the southern coastal regions of the North Sea, a very remarkable 

 difference between the winter months (December to February) and the spring and 

 summer months, (March to July) the percentage in winter of large plaice, over 35 cm. 

 being much higher. This is no doubt due to the fact that the small plaice hibernate 

 hidden in the ground, and thus escape being caught by the trawl. 



The following table (Tab. 2) and the graphical representation of same (Fig. 4) 

 giving the size and composition of the English landings from the whole of the North 

 Sea, divided according to months, present a good view of these monthly variations. 



From these it will be clearly seen, that the largest landings of plaice fall in the 

 spring and summer months, the smallest in the winter months: between summer and 

 winter there is also a slight increase in the quantities landed, viz, from September to 

 November. And here it is of particular interest to note, that the percentage in weight 

 of the market-class «small» in the landings increases and decreaises regularly with the 

 absolute quantity of the latter, as also the percentage in number of the «small» plaice 



