Translation Series No.1211

• of
•
fishing representsavalue for the measure of the exploitation that is
necessary, but not sufficient. It has to be supplemented by statements
about the strength of the stock or about the population density. The "eap=.
cebk
leue..e per unit effort" is customarily used as such a measure. It stands in
close connection with the effort. If we put this in relation to the yield
obtained, we shall have statements that are directly comparable with etich
cate.k.
other. We call the yield per unit of the gear employed the aretliee per
unit effort. In the present case it will be given as the number of salmon
per 1000 hooks or per 100 nets.
This unit hés already been used for the determination of the
effort and in the course of this work we shall have to come back to it
frequently in order to explain phenomena or to make them clearer. For this
are extraordinarily important. The fact alonè •
ct,td,„
. that the captuTe per unit effort is to be considered as a measure for the
strength of the stock, demands a critical analysis when ascertaining these
data. To begin with, it has therefore to be examined whether the results
• of the catch are being influenced by factors that have their cause not in
the stock. In.Other words: is the capture per unit effort a value that is
composed of several factors of which the strength of the stock of salmon
is only one? •
Let us consider for a start the monthly changes in the oebliàe
per unit effort. We must expect during the course of the season a steady
reduction of the stock through fishing and other effects. As far as the
catches
strength of the. stock ié concerned, the ceptueas per unit effort should:•
diminish steadily from fall to spring.
However, the monthly. trend in Table 7 does not show such a
.course. The values of the line.fishery rather rise until December, those
. ,
in the net fishery xise in part until February, only to fall until 'June
•
reason, these statements