Translation Series No.1211

•
N„
Z o = cf„ (M1- T) -- In — 1
No.
cf„ -(M+T) =- In NI +
N o
In NI cf„ (M+T) —
----i--- (Z — Z1)
`)
1
(f0 f1)
1
(fo f1)
N 1
In ° — 2 c U 0 17 f + (g+T)
— 208—
Paloheimo has established that his linear equation is superior
to the iterative method in all bases when deviations are introduced through
ceta-
defective material (age, c-ape per unit effort, figures for landings)
or through changes in c. The cause for this is to be seen in the fact that
Z 1 is not being correlated with f 1 but with 1/2 (f 1 + f 2 ). An improvement
can only be expected when c is strictly constant and when only the cep—
P. 353]
tuegs per unit effort per age group are erroneous. In all .other hypothet-
ical cases the standard deviation of c and M was reduced by from 27 per
cent to 69 per cent in comparison with the iterative method. The application
of the linear equation of Paloheimo to the values of Table 54 results in
the equation
Z2 = 0.2135 f + 0.288.
Since Z 2 7 1.23 on an average for the years 1956/57 to 1961/62
. we obtain (line catches):
Z,
(M + T) 2
1.23
0.29
F
2
0.94
The total mortality that has been obtained with the aid of the
netting values Can also be dorrelated with f according to the method of
Peoheimo.
Z 2 1.03
(M + T) 2 0.28
F 2
0.75
(7)