Translation Series No.1211

•
- 207 -
by changes in the intensity of fishing f, or the scatter of the values of
Z and f (that is, their error) is so large that the method remains without
success.
On the' other hand, Christensen (1964) was'able to obtain with
the aid of the iterative method results of F 2 = 0.73 and (M + T 2 ) = 0.60
(cf. 7.2.1.). If we now compare the data on which the two cases are based,
in order to find an indication of possible sources for errors, we find that
the correlation of the values for the -e-ap-te per unit effort (line) gives
a correlation-coefficient of rc = +0.93. There is also a high correlation
with ra = +0.94 between the two determinations for the age composition
c.lutbi-
e-84 per unit effort of A.1+). On the other hand the correlation Coef-
ficient for the values of the fishery expenditure is considerably lower
with rf = + 0.82. This indicates that the German figures for the fishery
expenditure do not represent the total expenditure with sufficient exactness.
'Faloheimo (1961) has developed a linear equation that makes un-
necessary the iterative method in the determination of F and (M + T). For
this purpose the second term in equation (6) has been set . K. When
- ln 7 aZ, then
aZ 1
+ aZ o'
The equation is decisively transfoimed through the determination
of a. For the calculation of the infinite series of
•
- 1.11
-Z
1-e
only the first term was used, whith the . result that a = 1/2. For Z.c1 the
error in - a = 1/2 is less than 10 per cent. Since the value of the second
term in equatiOn (6) is small compared with the first term, this approx-
imation may be permissible. Equation (6) then becomes;