262 



The Common Eel 



on this account escape detection. This is certainly a matter well 

 worth investigating. 



To catch the eels on their downward course and allow them to 

 escape on their upward is not a wise procedure, for by the time they 

 are going seawards they have done all the damage they can do, 

 while if caught on their upward progress a marketable size two or 

 three years old could be got. This arrangement would prevent an 

 enormous destruction of salmon fry, for I consider the eel by far the 

 greatest enemy that salmon and trout have. The young of the salmon 

 hide under stones during the winter, and an eel after a fish is like a 

 ferret after a rabbit it can not only go wherever a trout can go, but 

 its body remains concealed under a stone, with only its mouth and its 

 eyes exposed to view. There he lies in wait for any living thing that 

 comes near him. 



Not until April 1906 was it known where eels spawned. Professor 

 Grassi, of Rome, discovered the breeding-ground to be out in the 

 Atlantic Ocean from Norway, Denmark, France, and Spain, in some 

 parts 1000 miles from shore, at a depth of 560 fathoms, with the 

 eel larvae 50 to 100 fathoms overlying this depth. The generic 

 name " Leptocephalus " was applied to the eel larvae before their 

 history was known. 



The Leptocephalus develops from the egg, grows to the length 

 of about 3 inches, then ceases to feed until the metamorphosis 

 is complete and the little fish has become an elver. These larvae 

 have perfectly clear ribbonlike bodies, which are as transparent as 

 glass, and free from colouring, except in the case of the eyes, which are 

 black. Their length is about 3 inches and their breadth three-eighths. 

 The metamorphosis takes place in four stages, and when complete 

 the length is reduced to about 2^- inches, and the width to a little more 

 than one-eighth. When in the sea they are known as glass elvers, 

 but on arriving in fresh water pigment is developed in the skin and 

 they are now known as elvers. The times of migration to our shores 

 vary very much. In some localities it takes place in December, and 

 in others not till April. In the Shannon district it is as early as 



