46 THE BIOLOGY OF THE SEASONS 



The area on the continental slope away to the west 

 of the English Channel is regarded as the most northerly 

 of the main spawning places of the eel in the Atlantic, 

 and it is very interesting to notice that the recorded dates 

 of eel-fares in the various British rivers correspond approxi- 

 mately to the distances from the main spawning ground. 

 To give a few illustrations, " the elvers first appear at 

 Spain and far south at the French west coast (at Bayonne), 

 namely, in the last months of the year (October to December), 

 somewhat later farther north on the French west coast 

 in January, still more to the north in February, and in the 

 Channel in February to March. In South- West England 

 (Bristol Channel) the fishery also begins in February, or 

 rather in March." On the Danish North Sea coast the 

 ascent of the elvers begins in April or May, on Scottish 

 rivers, like the Tay and the Dee, it usually begins in May. 

 This is, of course, but a sample of the evidence that has 

 accumulated to show that the date of the eel-fare corre- 

 sponds, on the whole, with the distance the young eels have 

 had to swim from their spawning place. They are ready 

 to start about November, but they do not reach the Katte- 

 gat till May after a long journey. The discovery of the 

 spawning grounds has also explained why such colossal 

 numbers of elvers are sometimes seen in the Severn the 

 arms of the Bristol Channel form a huge trap for a large 

 contingent of the main migratory host. 



What happens in the case of the common eel seems 

 to be paralleled in the case of the conger. It is a more 

 southern form, and its larvae do not come farther north 

 than Rockall. The Leptocephali do not occur over such 

 great depths as those of the eel, but there is the same sort 

 of metamorphosis and the same sort of shoreward migra- 

 tion. But the conger remains in the sea. 



As we began by noting, the elvers pass up the rivers 



