Translation Series No.1211

Table 19. The share of sea trout in
the salmonid catches in
the Baltic Sea proper.
Weightéd
Season Denm. Germ. Pol. me an
1956/57
1957/58
1958/59
' 1959/60
1960/61
1961/62
1962/63
Weighted mean
3,0
6,2 42
2,4 3,3 60 10,8
6,9 15,5 87 26,5
3,4 84
5,9 , 3,9 79 12,8
1,5 12,8 87 24,4
1 valid for January only; Danishand
Polish figures after Christensen
and Chrzan.
5 8
The cod plays the main
role as a genuine companion fish
in the salmon fishery. It is being
caught mainly with driftlines, very
rarely in nets (Table 20). The
fishermen are of the opinion that
the occurrences of salmon and cod
exclude each other and they cite
as proof that during a large catch
of cod only very few salmon are
being caught. Concerning this it
must be .said that a hook that has already been taken by a cod, can no
longer catch a salmon. Since there exists a food competition between the
two species of fish, it is possible that an effect of gear saturation may
be reached. According to the number x of the cod already hooked, we have
then a catch of salmon, not per 1000 hooks, but per 1000 x hooks. The
catches of salmon can be influenced in this way by the presence of cod.
Vice versa, the yield of cod can also be influenced by the salmon. There .
will thus become eàablished an equilibrium between the two species. A
shift will always occur when the population density of one species changes
in relation to that of the other.
[P. 260]
Effects of this kind can find expression in the ratio between
the salmon catches with lines and in nets (Table 9) because cod are hardly
cc..td.es
ever caught in driftnets. The falsification of the ceptueeQ per unit effort
of salmon can amount to a maximum cif . about± 0.5 salmon per 1000 hooks.
This possible error, however, has to be neglected, because the necessary
figures for a correction are not available,for all years.