Translation Series No.1211

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stock density can affect the catches per unit effort with driftlines and
driftnets. Hitherto internal (selection) and external (temperature and
food) causes have been discussed. Now we shall investigate a further ex-
ternal factor, namely the effect of the wind.
cecÂd.!..
In Table 10 the eep-teres per unit effort with hooks in various
fishing regions4 under different wind slpeeds and wind directions have been
assembled. The figures from fishing region 5 are based mainly on catches
of from 200 to 2000 salkon, those from the other fishing regions are based
on from 20 to 300 salmon. Unreliable data are given in Q.
The best catches in all fishing regions have thus been made under
stronger winds. Before we can test the significance of the differences in
the catches, we shall have to consider that the values of columns 7 and 8
(Table 10) did not originate in a uniform system. We have started from the
ceckes
basis that the ceetutaee per unit effort should serve as a measure for the
strength of the stock. When we now investigate the effect of the wind, it
can be established at once that variations in the strength in different
years can produce perhaps far greater variations than the effect of the
wind. Effects of the food supply and of the temperature conditions have
been demonstrated above and it is not impossible that still other factors
influence the size of the capture per unit effort. •
These deviations increase the scatter of the series that also
enters as a variable into the test equation.,In order to eliminate the
effect of the strengths.of the different year classes, the deviations of
the Values in column 8 from thogeof column 7 as percentages were used as
the Iasis for the test of significance.'
4 For the fishing regions see Fig. 6.
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