ATLANT. DEEP-SEA EXPED. 1910. VOL. III]. 



MURAENOID LARVAE. 



11 



of course, be looked at in the light of the discoveries 

 made previously in the Atlantic by Schmidt, from whose 

 work "Contributions to the Life-History of the Eel", 1906 

 (24) the following table is taken, showing period and place 

 of occurrence of the different developmental stages: — 



the larvae from two series of stations arranged from SW 

 to NE:— 



The first series extends from lat. 34° 44' N, long. 

 47° 52' W, to lat. 56° 33' N, long. 9° 30' W. We see 

 that the length of the larvae increases from Stat. 64 to 



Devel- 

 opmental Period of occurrence 

 stage 



Place of occurrence 



Mode of life 



1 

 2 

 3 

 4 

 5 

 6 



May to August or Sept. 



August and Sept. inclusive 



August and Sept. inclusive 



August to Nov. inclusive 



Sept. and Nov. to April or May 



May to July 



Atlantic ocean, West of Europe, in deep water 



> Atlantic ocean, or nearer the coasts of Europe 



Near the coasts of Europe in shallower water 

 Coasts of Europe in fresh, brackish, or salt water 



Pelagic 



Partly pelagic 



On bottom 



1 



In his paper "Remarks on the Metamorphosis and 

 Distribution of the Larvae of the Eel", 1909 (25) Schmidt 

 says on p. 15: "Stage I occurs in spring and summer, 

 especially in the early summer, the later developmental 

 stages (2nd to 4th) in the later summer, autumn and 

 beginning of winter, while the glass-eel period is in winter 

 and spring." The period of occurrence of the full-grown 

 and metamorphosing larvae taken by the "Michael Sars" 

 corresponds on the whole with the period of occurrence 

 of the larvae in the same developmental stages, previously 

 taken in the North Atlantic Ocean, one larva (no 28 in 

 table, p. 9) having been taken in April 19tli to the 

 north of Cape Finisterre, the others between July 12 and 

 August 5. 



As already mentioned, all the small larvae were 

 taken to the south and west of the Azores, and most of 

 the big ones to the north and east of those islands. This 

 distribution can hardly be regarded as casual, and we 

 may infer from this that the spawning places of the eel 

 are situated still further towards the South and West, i. e. 

 somewhere between the West Indies and 

 the Azores. We must at any rate suppose that the 

 small prelarvae were taken nearer the spawning places 

 than the full-grown and metamorphosing larvae. 



If this theory be correct, we must suppose that the 

 larvae move in a direction from SW to NE, the larvae 

 found farthest towards the SW being smaller (younger) 

 than those found farther towards the NE. The two 

 smallest prelarvae were taken at Stat. 64 situated farthest 

 towards the SW, whereas the two largest were taken at 

 Stat. 56, situated farthest towards the NE, and if we compare 

 the catches from adjoining stations in a direction from 

 SW to NE, we find that this rule holds good in all cases, 

 except for the stations close to the European coastal 

 plateau. The following table gives the average length of 



Stat. 90, and then decreases, this decrease being possibly 

 due to the commencement of retrogressive metamorphosis. 

 The second series extending from 31° 24' N, 34° 

 47' W to 36° 53' N, 29° 47' W, includes only small 

 larvae, which show a gradual increase in length. This 

 table is based on so few individuals that the averages 

 cannot be considered of great value. However this may 

 be, the facts fit into the working theory that the spawning 



Station 



Average length of the 





eel-larvae 



64 



44-5 mm 



62 



53-6 , 



88 



66 „ 



90 



77-2 „ 



92 



74-5 „ 



94 



74 



98 



71-5 „ 



52 



50 mm 



53 



52-4 „ 



56 



59-5 . 



ground of the eel is situated somewhere about 30° N 

 and 50° W, and that the larvae move in a north-easterly 

 direction towards the coasts of Europe. 



Through his comprehensive investigations Schmidt 

 has, in my opinion, shown that the eel has a certain 

 spawning period, which may possibly be protracted. 



If there were any way of fixing the age of the different 

 larval stages we should be a step nearer the solution of 

 the question as to when the eel spawns. 



The diagram on p. 8 strikingly resembles the groups 

 obtained when the youngest classes of other fishes, like 

 the herring or flounder, are arranged according to length, 



