49 



Tlie development of tlic plnice i/oung iu tlie uorthern Danish waters in 1904 

 was al)Out 1 mouth iu advance of the development in tlie western Baltic at Ærø. 



In 1904 we have so to speak found the plaice young iu all stages of 

 meiamorphosis. And this sliows, that nietamorphosis eau proeeed at or uear the 

 bottom in the neighbourhood of the coast. 



Flounder. Pleuronedes fiesus. 



Iu our 1904 collectious uo distinetion was made between the eggs of the 

 flounder and those of the dab. As regards the time and place ol appearauce of 

 the flouiider eggs, we must therefore be conteut to sa}', that tlie Jlounder-dah eggs 

 are found so to speak everywhere iu the Danish waters where we sought -for them 

 in the niouths of March — August (see Tab. 2). 



Pelagic floimder-yoimg were takeu by us in 1904 in April — June. 



We took thera the first time at the end of April. We went from Nyborg 

 on April 13th through the Great Belt and Kattegat with a detour into the 

 Lim Fjord. On the way we used the yonng-fish trawl a great deal but found no 

 flounder young. It was only on April 28th, wlien we were in the Skager Rak 

 (see Tab. 1), that we found a few, in all 3. When we again turned southwards 

 through the Kattegat, we found the flounder young everywhere, but they were small. 



In May we fouud many flounder young and almost equally many every- 

 where. Whereas the plaice young in April and May were especially numerous in 

 the Skager Rak and western Baltic, this was not the case with the flounder young 

 (see Tab. 3 B). On the contrary but few were taken in the Skager Rak, and the 

 western Baltic gave uothiug iu comparisou with the other waters. 



In June pelagic flounder young were still found, but not many, and at 

 the end of the raonth the pelagic life was quite over. 



The bottom-stages were lirst fouud on June 7th at Anholt harbour. From 

 the middle of June onwards we met the bottom-stages of the flounder so to speak 

 everywhere where we made investigations, yet as a rule only where the salt water 

 was somewhat mixed with fresh from outlets. There is uo boundary for the 

 flounder young in our waters as for the plaice, which separates the regions where 

 the bottom-stages are found from those where they are not found. 



The reasou for this difference in the distribution of the bottom-stages of 

 plaice and flounder is, that the flounder young are not so dependent during develop- 

 ment on the salinity of the water as the young plaice are. Further the eggs and 

 young of the flounder appear later in the year than those of the plaice. We found 

 the plaice young even in March, whilst the flounder young were first taken at the 

 end of April. The warmth of the water increases cousiderably from raonth to 

 month in the spring, and the iiatching of the eggs and the further development 

 proceeds more quickly iu consequence for the flounder than for the plaice. The 

 currents have thus not the same amount of iufluence on the flounder eggs and 

 young as on those of the plaice, and are also perhaps less strong during the pelagic 

 life of fhe flounder than during that of the plaice (conceruing these conditions see 

 "De danske Farvandes Plankton i Aarene 1898—1901", I. p. 2ri0). 



All the flounder young we have taken in intermediate hauls were symmet- 



7 



