Translation Series No.1211

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fish. The tagging does not give any information about the course of the
later movements until the fish ente r . the home stream. We do know, however,
through the analyses of the stock, that the age composition changes each
year beginning in April/May on account of the emigration of the spawning
fish. This is also clearly indicated by the reduction in the average weight
(Table17). The change caused by the emigration of the larger fish extends
into June.,(There are n4 data for July on account of the cessation of the
fishing.) It is, however, not known that the share of the large fish does
increase at this time On the fishing grounds 4 or 5, which have to be
crossed by the maturing fish.
Table 23. Number of salmon of more than 5 kg weight
on various - fishing grounds as percentage of
the total catch.
Bornholm
Month 58 .5.2 (60) 61 Mean 58 .52 60 61 Mean
59 60 (61) 62 59 60 61 62 •
Nov./Dez. 60 55 (27) 29 48,0 37 31 38 19 31,3
Jan./Febr. • 55 31 (44) 26 37,3 41 36 24 13 28,5
MârziApril 39 15 10 21,3 36 21 40 31 32,0
On the Pther hand, Table 23 indicates that the share of the fish
over 5 kg in weight in the catch near Bornholm diminishes during the course
of the season. This phenomenon could perhaps be explained by the beginning
of the emigration of maturing salmon.
Danzig Deep
Many papers have been published about the "homing" of the sal-
mon about to spawn. Especially important are the results of A. D. Hasler
(1954, 1960), who could demonstrate a "sun-compass mechanism" and, among
other things, a long-persisting olfactory memory in Pacific salmon. J. B.
Brett and C. - Groot (1963) speak of the innate ability in sockeyesalmon
(Oncorhvnchus nerka) to be able to keep s8..u. sun-compass diredeon and they