Fróðskaparrit - 01.01.2005, Page 104

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MIGRATION OF COD (GADUS MORHUA):
TAGGING EXPERIMENTS AT THE FAROES 1952-1965
the Faroe Plateau were classified as “accu-
rate homers” according to Robichaud and
Rose (2004).
The first tagging experiments with cod
at the Faroes were conducted between
1909-13 (Strubberg, 1916), and addition-
al taggings were performed in the 1920s
(Strubberg, 1933). The majority of the fish
were small (35-45 cm, 2 years) and were
recaptured very near the tagging site, i.e.
very limited migration. The fishing inten-
sity in the tagging area was very high, and
thus very few tagged fish reached sexual
maturity, thus leaving little information
about spawning migration.
Spawning migration was investigated in
tagging experiments during 1927-37, when
large cod (average size 80 cm) were tagged
at the main spawning site “Norðhavið”
during spawning in March-May (Táning,
1940). The results showed that cod left
the spawning area after spawning and were
fully dispersed around the Faroe Plateau
during summer and autumn. They aggre-
gated again at the same spawning location
in subsequent years, and the migration
distance ranged between almost zero to
about 120 nautical miles. No tagging was
performed on the western spawning site
“Vágahavið” (Táning, 1940; Jákupsstovu
and Reinert, 1994).
The tagging experiments in Strubberg
(1916; 1933) also showed that small, im-
mature cod usually were distributed in
shallow waters (< 100 m depth) whereas
mature cod (> 70 cm) frequently were
found down to 200 m depth (Táning,
1940), i.e. cod moved to deeper waters
when they grew larger.
The goal of the tagging experiments
in 1952-65 was to get more information
about spawning migration and to investi-
gate the migration pattern of cod, that was
not associated with spawning. A small part
of the material was published in Joensen
(1956), but the rest of the 1952-65 mate-
rial had to wait 40 years before it was pub-
lished in the current article. The reader
may wonder why so old results should be
worth publishing, but as stated earlier, the
migration pattern may change with time
and a thorough understanding of migration
patterns requires studies during different
time periods. When publishing other tag-
ging experiments (initiated in 1997, see
later), the 1952-1965 material may be
very valuable. In the interest of space, fish
growth is not dealt with in this article.
After the tagging experiments in 1952-
1965 (the current article), extensive Eng-
lish tagging experiments with cod were
performed during the period 1961-1967.
In total 11442 cod were tagged and 2141
recaptured. A part of the material is pub-
lished in Jones (1966), but migration was
only briefly dealt with.
In the period 1994-95, sea ranching
experiments were conducted with pen-
reared cod on Faroe Plateau and Faroe
Bank (Fjallstein and Jákupsstovu, 1999).
About 50000 individuals were released
on Faroe Bank, but only about 200 were
recaptured. On the Faroe Plateau, about
8000 individuals were released and about
1200 have been recaptured up to 2004.
They were released in shallow waters
(< 50m) in a sound between the two larg-
est islands. They dispersed from the sound