| dc.description.abstract | The material dealt with in this paper contains 975 specimens of
fresh-water eels from the Norwegian Skagerrack Coast. Of these specimens
674 (9 males, 665 females) were yellow eels collected in the sea
near the shore; the rest, 301 specimens, were taken in lakes and rivers
near the town of Arendal. Of the latter group 150 specimens (35 males,
115 females) were silver eels, 48 specimens (females only) were yellow
eels, and 103 specimens were young ones of indeterminable sex.
Attention is especially drawn to the two different types of yellow
eels, viz. broadheaded and narrowheaded ones. The measurements
(external head proportions in relation to total length and thickness
of the body) show a marked difference between the extreme specimens
of the two types, but also that they are well combined by intermediate
forms. Cranial measurements of young eels show the same variation
as the external head measurements in larger eels.
By counting the vertebrae in typical specimens no difference in
this character was found between the two types.
By changing from yellow eel to silver eel the body increases very
much in thickness; measurements show that this fact is sufficient to
account for the relatively narrower head in the silver eel.
The size of the eyes by changing from yellow eel to silver eel increases
by 62 per cent in the males, 39 per cent in the females.
The analysis of the stomach content of the eels from the sea shows
that crustaceans, and partly small fishes, are the most important food
animals. To a certain degree the broadheaded eels prefer fish, the
narrowheaded ones crustaceans.
In fresh water insect-larvae of different kinds together with small
snails constitute the main food of the eels. | |
