Translation Series No.1211

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already been pointed out several times (T.H. Jgrvi 1938,.B. Dixon 1954 ,
F. Chrzan 1959b, F. Thurow 1960).
5.4.2. Discussion of the findings
A. Lindroth (1961a) has ascertained in his extensive analysis
of the iaaterial of Jârvi that the size of a fish at a certain age is det-
ermined by font. factors,.namely, the genetically fixed growth potential,
the intake of food, the chemical and physical environment (especially tem-
perature) and'the initial size that it had at.a certain time. The last
point is obviously valid only when a limited period of life is under con-
sideration. As in the present case, the life of salmon in the sea. Apart
from the innate growth potential the three points are not primary factors.
In . their changes they are rather subject to other factors. Thus, for ex-
ample, the intake of food depends on the numbers of prey available, on the
time of their appearance and on the number of competitOrs for the food.
5.4. 2. 1. The rate of growth
Before we consider some phenomena that are indicated'by the
matérial presented, the general features of the growth process must be
reviewed. The course of both the increase in length and in weight shows
that the rate of growth dScreases considerably during the fourth year in
. the sea. It is a general feature Of fish that they grow during their,entire
life. Only in rare cases, when they, are forced to cease feeding, is it
possible for the weight to decrease. .
11). 329]
In the treatment of the salmon with spawning marks it has been
éstablished that the sea year class A.3+ (that of the fourth year in the „
Baltic Sea) cc:insists already . Of 37 per cent of salmon with spawning marks.. .
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