THE BREEDMU OF THE NORTH ATLANTIC FRESHWATER-EELS
163
bers of eels (Johansen, 1929). The eel is simply the species of the
Danish salt-water fishes which suffers most from severe winters ;
several other species, like Qobius niger L., Coryphopterus jIaveacena
(Fabricius), Solea soka L. and others, may also suffer, but the important point is that among the eels both silver eels and yellow eels are
kilted.
Furthermore, bacterial diseaaes quite often cause mass kills, and
great losses to the fishermen (Bergmann, 1909, 1912 ; Schiiperclaus,
1927, 1934 ; Bruun and Heiberg, 1932, 1936 ; Nybelin, 1936).
Tucker (1969a, p. 497; 1959b, p. 1408) seems to assume that the
European eel dies off mass-wise not very far from the mmts ; Schnakenbeck‘s (1934) specimen, with complete occlusion of the vent, from the
North Sea “ is to be taken as representing the state attained in European continental waters by eels which survive thus.” In view of the
many marking experiments, showing recaptures of eels which have
migrated 600-600 nautical miles, this seems & rather sweeping statement, also because Schnakenbeck’s specimen was only one out of four,
and that nobody else ever reported on a similar specimen.
If there really were a mass-mortality in European continental
waters, not least in the North Sea and the English Channel, such a
yearly occurring phenomenon would certainly have been observed.
In nature weaklings and dead animals are rarely left to rot on the seafloor ; they are eaten. This has, in fact, also been reported after cold
winters in Denmark. Johansen (1929, p. 91) reports a remarkable case
of a cod (Gadus mrrhucc L.), 89 cm long, containing eight large eels;
this is remarkable because the cod gencrally cannot catch large eels, so
they must have been weakened by the cold. Johansen also cites a
letter from a fisherman, who states: “ The eel is the fish which suffers
most here during ice-periods. When fishing operations are carried on
with the Danish seine or otter seine on the last few days before the
water is covered with ice, the cod which am caught are full of eels, and
feeble eels are now and then taken up with the seines. The same OCCWH
just after the ice has gone.”
The sperm-whale is no scavenger so even if Vaillant’s observation
(1898) is unique so far, it is not contrary to the idea that healthy silver
eels do occur in the open Atlantic, in this case in the vicinity of the
Azores.
Another observation pointing to a pelagic life of the silver eel is found
in the classical paper of Grassi and Calanhccio (1897, p, 427), here
translated from the German : “ Eels . . . are also found in the stomachs
of sword-fishes, caught in the Straits of Messina. They even seem to be
their favourite food.”
163
bers of eels (Johansen, 1929). The eel is simply the species of the
Danish salt-water fishes which suffers most from severe winters ;
several other species, like Qobius niger L., Coryphopterus jIaveacena
(Fabricius), Solea soka L. and others, may also suffer, but the important point is that among the eels both silver eels and yellow eels are
kilted.
Furthermore, bacterial diseaaes quite often cause mass kills, and
great losses to the fishermen (Bergmann, 1909, 1912 ; Schiiperclaus,
1927, 1934 ; Bruun and Heiberg, 1932, 1936 ; Nybelin, 1936).
Tucker (1969a, p. 497; 1959b, p. 1408) seems to assume that the
European eel dies off mass-wise not very far from the mmts ; Schnakenbeck‘s (1934) specimen, with complete occlusion of the vent, from the
North Sea “ is to be taken as representing the state attained in European continental waters by eels which survive thus.” In view of the
many marking experiments, showing recaptures of eels which have
migrated 600-600 nautical miles, this seems & rather sweeping statement, also because Schnakenbeck’s specimen was only one out of four,
and that nobody else ever reported on a similar specimen.
If there really were a mass-mortality in European continental
waters, not least in the North Sea and the English Channel, such a
yearly occurring phenomenon would certainly have been observed.
In nature weaklings and dead animals are rarely left to rot on the seafloor ; they are eaten. This has, in fact, also been reported after cold
winters in Denmark. Johansen (1929, p. 91) reports a remarkable case
of a cod (Gadus mrrhucc L.), 89 cm long, containing eight large eels;
this is remarkable because the cod gencrally cannot catch large eels, so
they must have been weakened by the cold. Johansen also cites a
letter from a fisherman, who states: “ The eel is the fish which suffers
most here during ice-periods. When fishing operations are carried on
with the Danish seine or otter seine on the last few days before the
water is covered with ice, the cod which am caught are full of eels, and
feeble eels are now and then taken up with the seines. The same OCCWH
just after the ice has gone.”
The sperm-whale is no scavenger so even if Vaillant’s observation
(1898) is unique so far, it is not contrary to the idea that healthy silver
eels do occur in the open Atlantic, in this case in the vicinity of the
Azores.
Another observation pointing to a pelagic life of the silver eel is found
in the classical paper of Grassi and Calanhccio (1897, p, 427), here
translated from the German : “ Eels . . . are also found in the stomachs
of sword-fishes, caught in the Straits of Messina. They even seem to be
their favourite food.”