APPENDIX E: HEINOKE _ 22 — 



(2) The plaice may wander very quickly at times from one region to 

 another. The two plaice which had gone from the Horns Reef into the Norderney 

 district (c. 88 s. m.) in 28 days, had travelled daily on an average not less than 3 s. m., 

 and this holds good also for a plaice which had wandered from the Horns Reef towards 

 the Skager Rak, ca. 120 s. m., in 43 days. 



To obtain certain conclusions here, many more plaice must be set out yearly than 

 has hitherto been the case, and the experiments must be continued over a larger number 

 of years. 



The question whether two or more distinct local races of the plaice exist in the 

 North Sea, has not as yet been closely investigated by us. We have, nevertheless, some 

 grounds for believing, in agreement with English naturalists, that two races occur, viz. a 

 southern plaice, extending from the English Channel to Heligoland, and a northern 

 plaice, extending from Heligoland to the North, the first of which is constitutionally 

 smaller than the second. We have once received spawning plaice of very small size, 

 caught at Borkum by a German sailing cutter in the month of March; one female with 

 running spawn, measured only 22 cm. 



Speaking in general from our experiences, the biology of the plaice in the 

 eastern parts of the North Sea presents the following picture. The spawning of the 

 eggs takes place on wide areas from the 20 to the 40m. line and even further out; from 

 these areas, the larvse, when they approach the end of their metamorphosis, wander — at 

 least the great majority do — iiito the warm, shallow waters close to the shore and pass 

 the youngest bottom-stages there. From the end of their first year onwards, the young 

 plaice migrate gradually in a mass, as they become larger and older, further out to sea 

 into greater depths, and one finds, furthest from land in the open sea, scarcely any but 

 the older groups of 5 years and over. 



2. The flounder [Pleuronectes flesus) 



The eggs and larvae. 



The data concerning these are not quite exact, in so far as the eggs could not always 

 be distinguished with certainty from those of the dab and the sprat, nor the larvse from 

 those of the dab. 



In our vertical hauls during the March cruises, 91 eggs and 79 larvse were taken 

 altogether. Thus, the spawning period for the flounder seems also to be over, for the most 

 part, in March. At Heligoland, we found flounder eggs from the end of January to the 

 middle of April.. In agreement with our earlier observations, the main quantities of the 

 eggs and larvse were met with over depths of 20 to 40 m., yet nearer the 20 than the 

 40 m. line, thus somewhat nearer land than for the plaice. They were found in this zone, 

 both in the southern and northern parts of the region fished, as far as Skagen , and 

 especially numerous N.W. from Heligoland. Beyond the 40 m. line, they occurred but 

 rarely, and not at all in the open North Sea. 



Older larvse (in the metamorphosing stages) were not yet noticed in March. They 

 appear, however, in the plankton at Heligoland in the second half of April and beginning 

 of May with greater regularity, and are 9 to 12 mm. long. Similarly, isolated specimens 

 were found during the seasonal cruise in May e. g. on the outer Jutland Bank on the 

 40 m. line. In May, the older metamorphosed stages are already met with in brackish 



