DISCOVERY 



255 



The Migrations of 

 the Eel 



By G. P. Farran 



In a paper recently published in the Transactions of 

 the Roval Socielv of London, Dr. Johs. Schimdt, the 

 Danish zoologist, has given us almost the last word 

 in the answer to the riddle : " Where do eels come 

 from ? " which for some thousands of years has excited 

 the curiosity of mankind. Strange as have been the 

 theories put forward from the time of Aristotle to the 

 present day, the truth as disclosed by Dr. Schmidt is 

 no less strange. 



Curious ribbon-like fishes, about 2 J in. long, clear 

 as glass, with pointed head and tail and opaque 

 silvery eyes, to which the name of Leptocephali has 

 been given, have long been known in the Straits of 

 Messina, where they were brouglit to the surface in 

 considerable numbers by ascending currents and 

 whirlpools. These fishes came in time to be regarded 

 as the larvae of eel-like fishes (abnormal forms according 

 to one school of thought), but it was not until 1S93 

 that the Italians Grassi and Calandruccio, as recorded 

 by the former in a paper, also read before the Royal 

 Societj', definiteh' recognised, by rearing it through its 

 later stages, that the form known as Leptocephahis 

 hrevirostris was in reality the larva of the common eel. 

 It was at this stage in our knowledge of the eel that 

 Dr. Schmidt started his work by the capture, to the 

 west of the Faeroes, in May 1904, of the first specimen 

 of Leptocephahis hrevirostris known in the Atlantic. 

 A second specimen, as Dr. Schmidt records, was taken 

 three months later off the west coast of Ireland by the 

 Irish fishery cruiser Helga. 



We may here review briefly what is kaiown of the 

 eel during its sojourn in fresh water. The eel, when 

 feeding and growing, is characterised by its greenish 

 back, yellow belly, broad head, and small eyes. 

 Formerly in this stage it was regarded as a distinct 

 species, and was called the frog-mouthed eel or yellow 

 eel. When the adult or migrating stage approaches, 

 which may be reached by females after a stay in fresh 

 water of from five to twenty years, with a length of, 

 usually, from 2 to 3 ft., and by the much smaller 

 males after five or six years, with a length of not more 

 than 20 in., a change begins to show itself. The 

 powerful jaw muscles, which gave the head its broad 

 appearance, begin to shrink. The head gets more 

 pointed, the eyes increase in size, and the yellow 

 colour changes to silvery, the eel thus becoming what 

 is known to fishermen as the sharp-nosed eel or silver 

 eel. With this change of form and colour the repro- 

 ductive organs begin to develop, and the eels start 



on their journey seawards in autumn and winter. 

 From the pools and lakes of all the countries of 

 Europe they make their way downwards by streams 

 to the larger rivers, and thence to the sea, resting bj' 

 day and travelling by night, the principal runs taking 

 place on dark moonless nights. This is the season 

 when a heavy toll is taken of them by fishermen at 

 the eel weirs with nets or traps set with their mouths 

 pointing up-stream. In the countries bordering on 

 the Baltic, especially in Germany, Denmark, and 

 southern Sweden, the migrating eels, after they have 

 reached the sea and are making their way along the 

 coast towards the entrance of the Baltic, are taken 

 in large numbers in traps set along the shore. 

 Professor Peterseii states that there are no less than 

 22,608 of these traps on the Baltic coast of Denmark. 



DIAGRAMM.\TIC CH.\RT SHOWING THE BKEEDIXG PI,.\CE OF THE 



ElfROPE.'U^ EEL, AND THE AGE IX YEARS OF THE I.ARV/E AT 



DIFFERENT STAGES OF THEIR JOURNEY TO THE EUROPEAN 



COAST. 



From marking experiments the rate of travel of these 

 coasting eels has been estimated at about ten miles 

 a day. 



On its arrival at the open sea we lose sight of the 

 migrating eel, which never returns. It is true that a 

 few chance specimens have been taken, one in a 

 trawl net near the mouth of the English Channel, 

 another in the stomach of a cachalot in the Atlantic, 

 and others in the Mediterranean, either taken from 

 the stomachs of sword-fishes or brought to the surface 

 by the whirlpools of Messina ; but detailed knowledge 

 of how they travel, whether in mid-water or along the 

 bottom, and what they feed on, if they feed at all, 

 is still lacking. These eels from the ocean show a 



