Translation Series No.1211

- 140
-
that have been analysed there was not a single salmon that had lived in
the Baltic Sea for more than six years. The fishery rests thus principally
on the two sea year classes A.1+ and A.2+, which account on an average for
almost 97 per cent of the yield.
If we cômpare these results with the statements by other authors
(Talle 34), we find that the sea year class A.2+ was exploited the heaviest
until the season of 1952/53, when it brought about 60 per cent of the yields.
The classes A.1+ and A.3+ accounted together for a further 38 per cent.
The picture changed considerable during the subsequent years, so that the
sea year class A.3+ played practically no longer a substantial role, while
the main share shifted from the fish of three winters (A.2+) to those of
two winters.(A.1+).
It must be obvious that the analyses of captures until 1953 •
cannot have given a true picture of the conditions of the stock. Under
average 'conditions the sea year-class A.+ must have the highest number of
individuals in the stock, whereas the number of fish in the following sea
year classes diminishes steadily through fishing and natural waste and
the emigration to the spawning grounds. A. fishery that is exploiting the
stock representatiVely, must also reflect these relations.
Although F. Çhrzan (1959b) has examined-only an average of
160 salmon, a possible error may have been compensated through the for-
[1:4 313]
mation of mean values. He hils established that the changes in the compos-
ition of the catches around 1953 are connected with the use of smaller
fishing hooks. The Polish fishermen changed during this time from hooks
-with an opening of 25 mm to those with an opening of 13.5 and 15 mm.:Since
• at that time.the bait-for the large hooks consisted of herring, it is'pos-
sible that significant differences occurred between the catches with the'