— 9 — APPENDIX H: GARSTANÜ 



On the Ameland Gronnd experiments were carried out by the English investigators in 

 December, 1902 (no 9 on the chart). In tlie three following months the fish were recaptured 

 along the whole length of the Dutch and Belgian coasts from Ameland to the Hinder. In 

 April and May they were recaptured in two groups, one near the original point of liberation 

 and another in a distinct band between Yarmouth and Helder corresponding with the fishing 

 grounds known as the Texel Ground, the Brown Bank and the regions near Smith's Knoll. 

 In July to September the separation between these two areas of recapture became still more 

 evident, the one group being distributed over the Terschelling off-grounds as far northwards as 

 Clay Deep, and the other in the region between the Brown Ridges and the Leman Shoals. 

 The size of the fish on liberation recaptured in the Terschelling area was distinctly smaller 

 than that of the fishes found off the English coast. The explanation of the facts is fairly 

 clear. In January to March the largest fislies travelled the greatest distance from the point 

 of liberation, so that the general size of the migratory fish iji the southern half of the area 

 was higher than that in the northern region. The English experiment no. 4 (14 on the 

 summer chart) has already shown that the tendency of the plaice in this area during the 

 spring time is in a northerly direction. Thus the plaice recovered between the Brown 

 Bidges and the Leman Shoals in July to September are to be regarded in part as fish which 

 had reached a more southern point during the preceding winter and gradually congregated 

 in the north-western part of the area. Doubtless a considerable number of the fish had also 

 migi-ated directly offshore during the spring months from the Egmond Grrounds and the 

 Broad Fourteens. On the other hand the small fish recaptured on the Terschelling Grounds 

 during July to September are to be regarded rather as fish -which had merely sanded themselves 

 in the same region during the previous winter, to begin their offshore migrations in the fol- 

 lowing spring. 



Experiments carried out on the Leman Ground (no. 11 on the chart) showed the same 

 southward tendency of the majority of the plaice during the winter months, although a certain 

 number migrated short distances to the northwards. The Leman ground is, however, on the 

 line of division between two different natural areas, for along the English coast from the Wash 

 to Berwick a northward tendency of plaice in winter clearly preponderates (cf. experiments 12 

 and 16 on the chart). 



Speaking generally we may thus say that in the eastern and southern parts of the North 

 Sea the plaice evince a distinct southward tendency in the winter months, which becomes reversed 

 into a northward offshore tendency during the spring and summer. On the other hand the 

 tendency on the western side of the North Sea, north of latitude 53°, is distinctly northward 

 in the winter time. 



4. Intensity of fishing 



Owing to the fact that many of the plaice liberated in the course of the mai-king experi- 

 ments were scarcely of marketable size, and in consequence of the fact that the smaller plaice 

 are more liable to be injured by the process of marking than are the larger fishes, it is 

 desirable to exclude tlie smaller fishes from consideration in any use that may be made of the 

 marking experiments to determine the intensity of fishing under modern conditions. The limit 

 of 25 cm. has been adopted in the present case, and the subjoined table shows the percentage 



Appendix H 2 



