37 



It will be seeu from Table 10, tbat the growtb in length l'or tbe males 

 is very small, wlien tliey bave reaebed tbe age of 5 years (scale-group 3), and 

 tbat all tbe iudividuals keep togetber extremely regularly in growtb, so tbat tbe 

 ordinary eurves eau be used to represent tbe separate groups. The growtb of the 

 females is shown in Table 11; it is only witb tbe 8tb year (scale-group 6) tbat the 

 annual iucrease in growtb becomes smaller; but it does not cease in specimens 

 whicb reach a greater age. 



Tbe difference in tbe size of the males and females, whicb tbus becomes 

 more and more evident with tbe increasing age of tbe fish, is naturally seen best 

 in tbe adult or silver eels (see Tables 12^14), where the largest male is 48 cm., 

 whilst tbe largest female is almost double: 85 cm.; — it will easily be seen also 

 from the numbers ou Table 14 tbat this bolds not only for tbe comparison of the 

 size of single specimens but also for tbe year-group as a whole. It will likewise 

 be seen tbat tbe males become adult or silver 1 year before tbe females, — and 

 in certain euclosed waters, as »Kilen« at Struer and in part Odense Fjord, where 

 tbe stock cousists almost exclusively of male eels, these become silver somewhat 

 earlier thau in the open and larger waters, where botb males and females live. 



Tbe questions were put forward at the beginniug of this paper: how many 

 years lie betweeu tbe two great migrations of tbe eel? How old are tbe silver 

 eels wben as adults they leave our waters? 



We are able now to answer these; the answer is somewhat different 

 according as we are dealing witb males or females. Of tbe former some few live 

 only 41/2 years in our waters (e.g. in Kilen and in Odense Fjord), the majority 

 bowever 51/3 — l^j^ years, so tbat about an equal number remain Sy, and 61/2 years 

 bere before they migrate as silver eels; much fewer 71/2 years; once I bave fouud 

 a silver male eel whicb was 873 years old. 



The females become silver later, scarcely before they are 61/2 years old, 

 the majority not before they are 773 J'ears, and many indeed only become silver 

 when they bave been 81/2 years in our waters. Even older female eels may be 

 found though they must be considered rare. The following brief hst gives infor- 

 mation on the age of some old silver female eels, their length and growtb; they 

 were all taken in traps in tbe Little Belt during the silver eel fisbery tbere in 

 October 1906. 



96 cm. 121/2 years old 5 % 



96 — IIV2 — — ca. 4 - 



96 — IIV2 — — 4 - 



87 — IIV2 — — 3 - 



86 — IOV2 — — 3 - 



We come now to the question of tbe growtb in tbickness of tbe eel, whicb 

 bas been occasionally toucbed upon in the preeeding pages. Tbus, it was men- 

 tioned on p. 18, tbat it appears from tbe scale-investigations, tbat tbe eel grows 

 very much in tbickness in the fourth and fifth years; in these years it grows so 

 very stout tbat a very broad part is formed along tbe back, whicb is covered 



