Fróðskaparrit - 01.01.2005, Page 106

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MIGRATION OF COD (GADUS MORHUA):
TAGGING EXPERIMENTS AT THE FAROES 1952-1965
Figure 1. The study area in the waters off Faroe Islands (located at approximately 62°N 7°W), more
precisely on the Faroe Plateau (ICES statistical rectangle Vbl). Faroe Bank (ICES statistical rectangle Vb2)
is a shallow area south west of Faroe Islands. The 200 and 500 m depth contours are shown.
English and Scottish trawlers who some-
times used rather imprecise locations like
“off Mykines” (a large area south, west and
north of the westernmost island Mykines).
In these occasions the most likely posi-
tion was set, partially based on the present
abundance and distribution of cod. Depth
at recapture was often recorded and may in
some cases not correspond perfectly to the
position of recapture. No attempt has been
made to correct position or depth. When
assessing fish age, otoliths were broken at
the middle and the yearly rings counted.
Data about tagged and recaptured fish
were written by hand. The fourth author
punched the data into an electronic for-
mat. The second author looked over all
data and corrected obvious errors, in co-
operation with the fourth author.
Statistics
Mann-Whitney U-test (Sokal and Rohlf,
1995) was used to test whether migration
distance depended on food.
A general linear model (GLM) - mul-
tiple regression (Sokal and Rohlf, 1995)
- was used when testing which factors (or
variables) influenced migration distance.
In multiple regression, one variable (in
this case migration distance, termed the
dependent variable) is explained by two
or more variables (in this case fish length,
tagging area etc.) which are termed the
independent variables. A basic assumption