FISHES OF THE GULF OF MAINE 



153 



2}j inches long in April are about 5 inches long a 

 year later, or about 2 years after their transforma- 

 tion. The winter rings on the scales have shown 

 that full grown adults of the European species are 

 from 5 to 20 years old, depending on food supply, 

 and other conditions; this is corroborated for the 

 American species by the fact that Dr. Hugh M. 

 Smith, former Commissioner of the United States 

 Bureau of Fisheries, found that a female, on the 

 way down the Potomac, was in her twelfth year. 



At the approach of sexual maturity, which takes 

 place in the fall, the eels that are in fresh water 

 drop downstream, traveling mostly at night. 

 They now cease feeding, as do those that have 

 been living in the river mouths, bays, and estuaries; 

 the color of the back changes from olive to almost 

 black, the ventral side turns silvery, and the eyes 

 of the males grow to twice their previous size. 

 Both males and females then move out to sea, 

 and it is not until after they reach salt water that 

 the ovaries mature. In fact, no perfectly ripe 

 female eel has ever been seen, and only one ripe 

 male (of the European species). 



So little is the life history of the eel understood 

 by our fishermen, that we again emphasize the 

 undoubted fact that no eel ever spawns in fresh 

 water. 



The eels drop wholly out of sight when once 

 they leave the shore; 68 no one knows how deep 

 they swim, but they certainly journey out beyond 

 the continental slope into the oceanic basin before 

 depositing their eggs. Schmidt has been able to 

 outline the chief spawning center of the American 

 species (from the captures of its youngest larvae) 

 as between latitudes 20° and 30° N. and between 

 longitudes 60° and 78° W.; i. e., east of Florida 

 and of the Bahamas south of Bermuda. But it may 

 also spawn (always in deep water) farther north 

 as well." 



The American eel spawns in midwinter, thus 

 occupying one to two months in its journey from 

 the coast to the spawning ground, for Schmidt 

 found very young larvae (7 to 8 mm.) in February. 

 Eels, like Pacific salmon, die after spawning, the 

 evidence of this beiag that no spent eels ha ye ever 

 been seen and that large eels have never been 



IS Large eels, on their seaward journey, have occasionally been caught by 

 otter trawlers in the western part of the British Channel, but we know of no 

 such occurrence on this side of the Atlantic. 



« See Schmidt (Ann. Rep. Smithsonian Inst., (1924) 1925, pp. 279-314) for 

 a readable account of the investigations which enabled him to chart the 

 breeding places and seasons of the American and European eels. 

 210941—53 11 



known to run upstream again. Smith suggests 

 that they probably "jellify" and disintegrate, 

 as the conger does. 



Eels (European) are among the most prolific 

 fish, ordinary females averaging 5 to 10 million 

 eggs and the largest ones certainly 15 to 20 

 million. It is doubtful whether eggs laid by the 

 American eel have been seen, or of the European 

 either, for that matter. 60 But it is generally 

 supposed that they float in the upper or inter- 

 mediate water layers until hatching. The larval, 

 so-called "leptocephalus" stage, like that of all 

 the true eels, is very different in appearance from 

 the adult, being ribbon-like and perfectly trans- 

 parent, with small pointed head; and it has very 

 large teeth, though it is generally believed to take 

 no food until the time of its metamorphosis. 

 These leptocephali of our eel, living near the 

 surface, have been found off our coasts as far north' 

 as the Grand Banks, but never east of longitude 

 50° W. 



Inasmuch as the breeding areas of the American 

 and European eels overlap, not the least inter- 

 esting phase of the lives of the two is that the 

 larvae of the American species should work so 

 consistently to the western side of the Atlantic, 

 and those of the European to the eastern side 

 that no specimen of the former has ever been 

 taken in Europe or of the latter in America. 



The American eel takes only about one-third 

 as long as the European to pass through its larval 

 stage; i. e., hardly a year, as against 2 to 3 years. 

 The leptocephali reach their full length of 60 to 

 65 mm. by December or January, when meta- 

 morphosis takes place to the "elver"; the most 

 obvious changes being a shrinkage in the depth 

 and length of the body but an increase in its 

 thickness to cylindrical form, loss of the larval 

 teeth, and total alteration in the aspect of head 

 and jaws, while the digestive tract becomes 

 functional. 



It is not until they approach our shores, how- 

 ever, that the adult pigmentation develops or 

 that the elver begins to feed, a change that is 

 accompanied by a second decrease in size. How 

 such feeble swimmers as the leptocephali find 



" Four eggs taken on the Arcturus expedition near Bermuda in 1925 wer» 

 provisionally identified as those of the American eel by Fish who has pictured 

 them and the larvae hatched from one of them (Zoologica, New York Zool. 

 Soc, vol. 28, 1927, pp. 290-293, flgs. 103-107). But the date at which they 

 were taken (July 15-17) makes it more likely that they belonged to some other 

 member of the eel tribe. 



