Translation Series No.1211

they take account of the annual changes in the stock.
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It is very diffult to find,,the age composition of the total yields
with the aid of the above results. Kàndler has indeed introduced a statis-
tics with six groups of weight (1-2 kg, 2-3 kg, 3-5 kg, 5-7 kg, 7-8 . kg and
pver 8'kg) for the landings at the Kiel Seafish Market, in which all sal-
mon are regiStered numerically (R. Kândler and M. Lâhmann 1957). Kândler
(19 6 1, 1963, 1964) has used the distribution of the groups for obtaining
the age composition. However, a division of the fish landed into the tWo
most important sea yearcaasses A.1+ and A.2+ with the aid of these statements.
is, however, necessarily subject to errors. This is owing to the annual diem.
ferences in growth and to changing sharesof the sea trout. In Table 19 it
had been shown that the percentage of sea trout in the catches varies
greatly and has amounted to an average of 3 to 15 per cent during indiv4.
idual fishing seasons. It is difficult to eliminate these fish because they
are not listed separately in the figures for the yields and their share
in the individual groups is not fixed.
'A division of the.salmon landed with the aid of the statistikos
9f the catches can be carried out in such . a manner that the fish under 5 kg
weight are assignèd to seai.year class A.1+ and the heavier fishto 1.1ti
The actual boundary isectordin:g to wsight . between the twO grouPs‘is, however t
not constant. It shifts during the course of every fishing season as well
'as from season to season.
It is possible to estimate the errors that OCCUT when the age
• composition is determined with the aid of the statistids of the landings.
This c an be done in the following manner: the complete catches that have
been investigated are being divided according to the weight of the fish.
TheSe series or measurements contain also seà trout (Table 42, colleen 3).