46 



wonderkuil in winter to their hearts desire, they have destroyed 

 thousands and thousands of little plaices, which otherwise would 

 have yielded precieus fish for their trawls. 



I said that the smal! est flat fishes of those I investigated 

 were plaices, and this perhaps might cause my assertion not to 

 be accepted. If it is true that the flounder is born in the 

 Zuiderzee and that the plaices enter it froin the Northsea, then 

 there is every reason to expect that the sinallest flatfishes obser- 

 ved there should be Sounders. Either the whole theory of the 

 swimming in of the little plaices is false — or it raust be pos- 

 sible to explain why no very small flounders have been taken. 

 The explanation which I can give is I believe quite sufficiënt: 

 I collected flatfishes only where they were sought with the 

 »kuil" nets, and with these nets fishing is only possible where 

 the depth is at least six or seven feet : this depth moreover 

 being necessary for my steaoaer to get board and board of the 

 fishing vessel. The very small flounders, however, dweil in much 

 shallower parts of the sea near the coast and this especially 

 in water of little salinity. In May I was a couple of times 

 successful in coUectiug with the surface-net a few very small 

 flounders (one raight as well call them flounder-larvae) and I 

 got also several specimens , as I fished with the surface-net 

 (8 June '88) in the Eems and in the Dollard : they were floun- 

 ders of 9 millim. and were still nearly quite symmetrical. They 

 lived in water of very small salinity (areometer 1.0025 at 15*|2° 

 Celsius) and they led in company with larvae of the herring 

 and of the smelt a pelagic life. Later on they prefer a sandy 

 bottom on a muddy or in general a soft and fenny ground: 

 for a rather large part the bottom of the Zuiderzee is of a softer 

 consistence and the plaice are very fond of it ^). To coUect the 

 smallest flounders in the Zuiderzee one ought to search the places 

 with sandy bottom near Harderwijk, on the Kamperzand and in 



1) Möbius aud Heincke mention the same in their very valuable little book on the 

 fishes of the Baltic, p. 93: «Die Goldbutt (plaice) lebt vorzugsweise auf schlammigem 

 Grunde"; p. 96: «Die StrufFbutt (flounder) lebt vorzugsweise auf sandigem Grunde." 



