208 Capt. S. E. Widdriugton on the Eel, 



The fish-market at Vienna is held on the river, well-boats 

 being moored to the shore, whence the inhabitants of that 

 luxurious capital are supplied with the most delicious fish 

 brought from all sides. These people informed me that they 

 drew part of their supplies of eels from Ulm, but that the 

 greater part came from Bohemia, consequently from the head 

 waters of the Elbe, which ought to be a still colder river 

 than either the Rhine or Danube ! This winter the thermo- 

 meter was at 19^^ at Vienna, whilst at Dresden I was told it 

 fell to 24° Reaumur. 



Now, assuming the case to be as I have stated, that the ha- 

 bitat of the genus is confined to the upper streams of the Da- 

 nube, we have the fact, that migration is not necessary to 

 them*, although it is certainly their habit in this country. It 

 must be remembered that Ulm is in a very cold country, 

 being considerably higher than Vienna. There can be little 

 doubt that the eels there hybernate in the mud. But why 

 do they not remove to the more genial region, and to the 

 admirable locality of the delta of that great river ? The reason 

 I take to be the following : the waters of the Danube may be 

 divided into three classes ; fi.rst, those of the Black Forest and 

 that vicinity, and those which fall into the river from the 

 left, towards Bohemia. These waters are more or less rich 

 and fat, and of the description which afford the most abun- 

 dant nutriment to fish, especially of the genus we have under 

 consideration. Below Ulm, however, a change soon becomes 

 visible ; the great tributaries from the Alps begin to pour in, 

 and soon alter the character of the water. These Alpine 

 streams may be divided into two classes, those which proceed 

 at once from the glaciers and the upper valleys, without meet- 

 ing with large lakes to filter and purify them, like the Rhine, 

 Rhone, and some others : these waters are charged with the 

 comminuted particles of the rocks they have passed over, and 

 are not only rapid, but have a peculiar strength and rawness, 

 which I consider, combined with the want of food, renders 

 them uninhabitable by the eel and by many other sorts of 

 fish ; even the trout are scarce and of bad quality which are 

 taken from them, and the only good trout in the Alps are 

 those from the lakes or the streams of the plains, where better 

 nourishment is afforded to them. The second class of Alpine 

 waters are those which have passed through and been purified 

 by the lakes, from which they issue clear, softer and warmer 

 than those we have mentioned. Even these rivers are not fa- 

 vourable to the propagation of fish in general, and I was sur- 



* A jiaper by Chr. Drewsen, on the Migration of Young Eels, is to be 

 found in Krciyei's Tidskvift, vol.i. 



