— 230 — 



There is no doubt further that a considerable number of the fry come into the North 

 Sea round the north of Scotland as well as through the Channel. This may be con- 

 cluded from the fact amongst others, that specimens have been taken already in January 

 on the northernmost part of the Scottish North Sea coast ^ But just as the quantities of 

 eel-larvae were found to be so much less off Scotland than off S. W. Ireland, there can 

 be little doubt that the North Sea gets the greater part of its young eels through the 

 English Channel. 



During the passage from the Atlantic to the North Sea the number of fry is naturally 

 greatly reduced as more and more fall out on the way, but some have not yet attained 

 foothold on the coasts, and of these some come north round the Skaw into the Danish 

 and Swedish waters, whilst others continue northwards up to the Norwegian coast, which 

 otherwise presumably for a great part gets its supply of elvers across from the northern 

 part of the North Sea. 



From the beginning of March on at any rate we can thus find considerable quan- 

 tities of pelagic eel-fry in the Danish waters within the Skaw, where the ascent from 

 the sea into fresh water takes place from April to the beginning of June. The pelagic 

 fry have been aken as far south as in the Sound and Belts, but further to the east in 

 the true Baltic the pelagic stages have not been met with 2, not even the earliest quite 

 metamorphosed bottom-stages, though somewhat older (larger) fry have been taken. 



The phenomenon may possibly be explained in this way, that a great part of the 

 fry cease migrating during the passage through the shallow and narrow^ Danish waters, 

 where the salinity of the water gradually sinks considerably, so that so far as the eel is 

 concerned similar conditions occur to those at the mouths of rivers in salter waters. The 

 remainder which is gradually greatly reduced then goes sooner or later to the bottom 

 and undergoes complete metamorphosis. They may pass some time here, and only later 

 perhaps when they have become larger do they migrate to the coasts or up into the 

 fresh water, which occurs as we know in the Baltic. 



The view we have reached from the consideration of the available data is thus, that 

 the eel-fry are not born nearer the North-European coasts than out in the Atlantic to 

 the west of Great Britain and France. From there they migrate into the coasts of West 

 Europe so as to reach as soon as possible the goal which is necessary for their 



1 That a portion at any rale of Norway's stock of eels is due to the young which come from the Atlantic 

 west of Scotland is very probable. This is indicated amongst others by the young glass-eels of Stage 5 men- 

 tioned on p. 214, which were taken as early as April 5 th by Dj". Nordgaard as far north as Saiten Fjord (see 

 Chart, Plate XI). Similarly, Dr. NoRDGAARD on January 28th, 1898 captured an elver of ca. 6 cm. in 

 brackish water at Bergen in Norway, which I have had the opportunity to examine. If it belong to the 

 earliest year's group, though I am not quite certain, as it was not well-preserved, then it must undoubtedly 

 like the specimens from Saiten Fjord have come from the spawning places west of Scotland or the Faeroes. 



2 It should be mentioned that I have found pelagic glass-eels at Iceland in April 1904 the only time we have 

 begun our investigations there so early. In the true inner Baltic on the other hand they have never been found. 

 This shows also, that it is the great distance through shallow and narrow waters from the inner Baltic to the 

 spawning places in the Atlantic which determines the matter. Iceland lies nearer to these and this is the reason 

 why the eel-fry can sooner reach there, where the ascent has been observed already in March, that is, earlier 

 than in Denmark. 



