638 



AMERICAN MUSEUM OF NATURAL HISTORY 



" The Breeding Places of the Eel," Phil. 

 Trans. Roy. Soc. London, 1922, ser. B., 

 vol. 211, p. 179. 



Principal literature 



Our knowledge of the life history of the 

 eel is largely due to the brilliant and ex- 

 tended researches of Dr. Johannes Schmidt 

 of the Carlsberg Laboratory of Copen- 

 hagen (cited as Schmidt, E. J. 1906.1- 

 1914.2). These papers are chiefly in 

 English and have been embellished with 

 excellent illustrations of all stages of de- 

 velopment. These researches have been 

 summarized in two general papers one of 

 which is cited as •Schmidt, E. J. 1906.1, 

 and the other is the very recent paper, 

 quoted above. ' 



For a map showing the geographical dis- 

 tribution of the genus Anguilla, see Meek, 

 A. 1916.1 (p. 158). 



Lite history of the Eel 



Because of the very lateness of these dis- 

 coveries, which have not yet entered fully into 

 general ichthyological literature, we feel justified 

 in giving the following somewhat extensive 

 summary, compiled chiefly from the papers just 

 mentioned (especially Schmidt, 1906.1). 



The first Leptocephalus to come to 

 the attention of naturalists seems to be 

 the specimen taken by William Morris 

 near Holyhead, England in 1763 and sub- 

 sequently described by Gmelin (J. F. 

 1788.1, p. 1150) a,s Leptocephalus morrisii. 



Subsequently numerous other speci- 

 mens of these small, translucent or glassy, 

 ribbon-like creatures, brought to the sur- 

 face by the whirlpools in the Straits of 

 Messina, came into the hands of natural- 

 ists and were known under the family 

 name of Leptocephalidae (Bonaparte). 



Cams (J. V. 1861.2), in considering 

 these fishes, recognized their true nature 

 as larval forms, and assumed that they 

 were probably the larval form of the 

 ribbon fishes (Trachypteridse) . This 

 conclusion was shown to be erroneous by 

 Peters (W. 1869.2), who demonstrated 

 that larval ribbon fishes were quite 

 different. 



Gill (T. N. 1865.9) had just expressed 

 the view that the Leptocephali are the 

 larvEe of eels (" Congers "), and that Lep- 

 tocephalus morrisii is the young of the 

 conger eel. This conclusion was also 

 reached independently by Dareste (C. 

 1873.3). Gunther (A. 1859.1, vol. viii, 

 1870, 1880.4) accepted Gill's view, but 

 thought that they were abnormally de- 

 veloped conger larvae, which view was 

 likewise accepted by Bellotti (C. Add. 

 1883.1). 



The actual proof of Gill's view was first 

 made by Delage (M. Y. 1886.1) who kept 

 a specimen of L. morrisii in the aquarium 

 of the Roscoff laboratory and observed 

 its transformation into a small conger, 

 9.3 cm. in length. 



The way was now paved for the dis- 

 covery of the larval form of the common 

 eel. Kaup (J. .J. 1860.4) had previously 

 described one of the Mediterranean Lepr 



tocephali as Leptocephalus hrevirostris. In 

 1893, the epoch-making discovery that 

 this form is the larval form of the common 

 eel, Anguilla vulgaris, was announced by 

 Grassi and Calandruccio (1892.1-1903.1), 

 who had found the necessary transitional 

 stages. 



Not until 1904 had any Leptocephali 

 of the common eel been observed outside 

 of the Mediterranean. In this year 

 Schmidt (1904.1) took a Leptocephalus 

 of the European eel west of the Faroe 

 Islands. A second specimen was taken 

 on the west coast of Ireland in 1904 by 

 Farran (Holt, E. W. 1909.1). Subse- 

 quently numerous larvse were found in 

 the northeastern Atlantic. Jacoby (L. 

 1867.1-1882.1) believed the breeding 

 ground to be off the coast in deep water. 

 Schmidt (E. J. 1909.5) found the south 

 Atlantic to be devoid of Leptocephali. 

 Hjort (J. 1910.1) and Lea (E. 1913.2) 

 suggested that the breeding grounds 

 would be found in the central Atlantic 

 between the Azores and the Bermudas. 

 Schmidt, from investigations in the open 

 Atlantic in the schooner " Margrethe," 

 1913, and with over 500 gatherings made 

 for him on board various cooperating 

 Danish ships, found that the Leptocephali 

 increased in number but decreased in size 

 as he went from Europe toward the West 

 Indies. Small sizes were found concen- 

 trated in a comparatively small area, ex- 

 tending from 22° N. to 30° N. and from 

 40° W. to 65° W.; the central portion 

 lying about latitude 26° N. or approxi- 

 mately equidistant from the Leeward 

 Isles and from Bermuda. This is the 

 breeding place of the eel. At this point 

 the smallest larvae were found concentrated 

 in considerable numbers. In his most 

 recent paper (" The Breeding Places of 

 the Eel," etc. p. 206), Schmidt has sum- 

 marized the breeding habits of the eel as 

 follows: 



"Spawning commences in early spring, lasting 

 to well on in summer. The tiny-larvse, 7-15 

 mm. long, float in water-layers about 200-300 

 metres from the surface, in a temperature of 

 about 20° C. The larvse grow rapidly during 

 their first months, and in their first summer 

 average about 25 mm. in length. They now 

 move up into the uppermost water-layers, the 

 great majority being found between 50 and^25 

 metres, or at times even at the surface itself. 

 Then they commence their journey towards the 

 shores of Europe, aided by the eastward move- 

 ment of the surface-water itself. During their 

 first summer, they are to be found in the western 

 Atlantic (west of 50° long. W.). By their second 

 summer they have attained an average length 

 of 50-55 mm., and the bulk are now in the cen- 

 tral Atlantic. By the third summer, they have 

 arrived off the coastal banks of Europe and are 

 now full-grown, averaging about 75 mm. in 

 length, but still retaining the compressed leaf- 

 shaped larval form. In the course of the autumn 

 and winter, they undergo the retrograde meta- 

 morphosis which gives them their shape as eels 

 and brings them to the elver stage, in which 

 they move in to the shores and make their way 

 up rivers and watercourses everywhere. . . . 

 The eels utilise their sojourn in fresh water to 

 feed and grow big, but the duration of their 



