FISHERY BOARD FOR SCOTLAND. 



THE DISTRIBUTION OF THE hiWfE OF THE EEL 

 IN SCOTTISH WATERS 



{With One Chart). 



By ALEXANDER BOWMAN, D.Sc. 



There is no more fascinating chapter in the history of marine 

 investigation than that which tells of the elucidation of the life stoiy 

 of our common fresh-water eels. Those two dominant instincts in 

 the life of a fish, viz., the instinct to feed and the instinct to breed, 

 compel our European eels to seek at one period of their 

 existence the fresh waters of our rivers and streams, in which they 

 feed and grow, and at another period for the purpose of breeding, 

 such utterly different physical conditions as the warm deep waters 

 of the Atlantic. One can understand now how a profound mysterv 

 surrounded the propagation of this species for so long a time, and 

 how such a mystery could not be cleared away save only by costly 

 oceanic exploration, and by the development of modern engines and 

 methods of research. 



Only within the last few years have the main facts of this story 

 been made clear, chiefly through the brilliant researches of the 

 Danish and Norwegian investigators. Dr. Johann Schmidt and Dr. 

 Johann Hjort, which researches followed and in a large measure 

 extended the discoveries of Professor Grassi in regard to the eels of 

 the Mediterranean, 



We now know that the fresh-water eels which inhabit the rivers of 

 Western Europe were born in mid- Atlantic over great depths, and 

 that they themselves, as they grow up, must seek again the deep, 

 warm, salt water before they can reach maturity and reproduce 

 their kind. The young larvae are found far out in the Atlantic, 

 and as they grow up into quaint, transparent, leaf -like forms 

 (Leptocephali) , are carried by the prevailing currents towards the 

 edge of the Continental plateau. There, outside the 1000-med:re 

 line, they are found as fully-grown Leptocephali during the summer 

 months, over the long stretch from the westward of the Faeroe 

 Islands to northward of the Coast of Spain. 



Towards the end of summer (August-September), these fully- 

 grown, leaf -like larval eels begin a retrogressive change, and, aided 

 again by the prevailing curi'ents, make their way towards the coast, 

 gradually assuming the fonn and appearance of an elver, or young 

 eel. 



It is clear, therefore, that the stock of eels in the rivers which flow 

 into the Baltic and North Sea must be derived from the Atlantic 



(2887) Wt. 1853/3—500—12/1913. 



