Translation Series No.1211

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It is found that the sexual figure for both sea year classes is very
different. It amounts to 0.446 ± 0.0195 in group A.1+ and to 0.260 ± 0.255
in group A.2+. This difference points to the fact that during the third
year in the sea at least as many males have migrated as females. The sexual
ratio can therefore not be considered as constant. Since the strength of
the year classes and with it the ratio between the two sea year classes
A.1+ and A.2+ changes annually, the sexual composition of the exploited
stock must also undergo this change. It is thus not the numerical ratio [ p. 263]
of the sexes in the total catch that deserves our special attention but
that in.the two age groups.
Since the sea year class A.2+ in the sea comprises 74 per cent
females) these must also predominate on the spawning ground. As has already
[19 . 264]
been explained, the missing males of this age class can be replaced by the
numerous emigrating younger males. This, however, does not provide the
solution for the problem of the sexual ratio on the spawning ground. When,
for example, two very weak year classes follow on an exceptionally strong
year class, then it must be taken into account that the younger males and
grilse of the two weak year classes are not present in numbers sufficient
for the females of the strong year class. Here nature has obviously taken
precautions through the mature parr; because these fish were not subject
to the strong depletion of the stock in the sea they are probably always
present in sufficient numbers in the rivers.
.
3.2. The conditions of the gonads
According to A. Backmann (1929) there are two conceptions com-
bined in the word "maturation": the process of the development from the
juvenile fish to the sexually mature one during its first period of life,'
'Which happens, only once, and the obtaining of sexual maturity (sexmsa