THB ARTIFIOIAL PROPAGATION OF MAEINE FISH
17
TABLE xu. SUPPLEMENTARY DATA BY DAEL ON THB: ~~nmrolrr, V~LOE OF
COD-FRY LIBERATIONS IN NORWEGIAN FIORDS. (After Dannevig and D A l ,
1907)
Ssndeledfjord
Hcuefjord
Larvae liberated Cod fry
L a m liberaled Cod fry
in the opring per haul
inthoping perhad
Sept.-Oct., 1003 .
None
4.8
None
1.9
July-AUg., 1904
.
33.6
33.7
10.9
None
- -
16.1
6.6
millions
Sept.-Oct., 1904 .
11.4
10
1.6
7.6
11.6
July-Aug., 1906
.
33
millions
millions
Sept,-Oct., 1906 .
Dahl (1909) investigated other fiords with a fine-mesh tow-net to
catch younger forms, and observed that when there was a scarcity of
cod fry, this scarcity was common to a large stretch of coast line;
when fry were abundant, this abundance could be seen everywhere
within a large geographical area. The addition of artificially-hatched
larvae to a locality seemed nowhere to influencle measurably the
relative abundance of littoral fry. From hydrographio observations
he formed the view that pelagic cod eggs and lmae did not strictly
belong to the fiords, but to the open sea.
Alf. Dannevig (1928) disputed the contentions of Dahl, particularly
regarding the exchange of fiord water with the open sea. He thought
the water masses in the fiords were localized to a considerable degree
and, from oxygen distribution, deduced that only the surface layers
participated in the general circulation. Since cod larvae seem to
prefer a depth of 10-30 m, he considered it unlikely that they would
be affected greatly by surface currents, and therefore could be
categorized as fiord stock.
Hjort's criticism of Norwegian hatchery practice was confined fo
the artificial propagation of the cod. He believed there were other
fish stocks, especially plaice, which might benefit from artifioial
Propagation, particularly if rearing techniques could be improved.
Dmevig's technique for cod was applied to plaice at the Trondhjem
hatchery, in 1908 and subsequent years. Nordgaard (1914, 1926)
mported the appearance of unusually large numbers of small phiin Trondhjemsfjord 2 yebra after liberations began, and inclined to the
17
TABLE xu. SUPPLEMENTARY DATA BY DAEL ON THB: ~~nmrolrr, V~LOE OF
COD-FRY LIBERATIONS IN NORWEGIAN FIORDS. (After Dannevig and D A l ,
1907)
Ssndeledfjord
Hcuefjord
Larvae liberated Cod fry
L a m liberaled Cod fry
in the opring per haul
inthoping perhad
Sept.-Oct., 1003 .
None
4.8
None
1.9
July-AUg., 1904
.
33.6
33.7
10.9
None
- -
16.1
6.6
millions
Sept.-Oct., 1904 .
11.4
10
1.6
7.6
11.6
July-Aug., 1906
.
33
millions
millions
Sept,-Oct., 1906 .
Dahl (1909) investigated other fiords with a fine-mesh tow-net to
catch younger forms, and observed that when there was a scarcity of
cod fry, this scarcity was common to a large stretch of coast line;
when fry were abundant, this abundance could be seen everywhere
within a large geographical area. The addition of artificially-hatched
larvae to a locality seemed nowhere to influencle measurably the
relative abundance of littoral fry. From hydrographio observations
he formed the view that pelagic cod eggs and lmae did not strictly
belong to the fiords, but to the open sea.
Alf. Dannevig (1928) disputed the contentions of Dahl, particularly
regarding the exchange of fiord water with the open sea. He thought
the water masses in the fiords were localized to a considerable degree
and, from oxygen distribution, deduced that only the surface layers
participated in the general circulation. Since cod larvae seem to
prefer a depth of 10-30 m, he considered it unlikely that they would
be affected greatly by surface currents, and therefore could be
categorized as fiord stock.
Hjort's criticism of Norwegian hatchery practice was confined fo
the artificial propagation of the cod. He believed there were other
fish stocks, especially plaice, which might benefit from artifioial
Propagation, particularly if rearing techniques could be improved.
Dmevig's technique for cod was applied to plaice at the Trondhjem
hatchery, in 1908 and subsequent years. Nordgaard (1914, 1926)
mported the appearance of unusually large numbers of small phiin Trondhjemsfjord 2 yebra after liberations began, and inclined to the