さあ！諸君！捕鯨問題だ！

次説じゃなく次節。
IWC年報は著作権を主張していない国際公文書なので
どんどんゆきます。
REP. INT. WHAL. COMMN 40, 1990, 　　 490頁

THE PRECISION OF ESTIMATES USING YEARLY
ABUNDANCE INDICES
As has been pointed out (e.g. IWC, 1989a; IWC, 1989b
p. 38; Holt, 1987; de la Mare, 1987 and 1989) determining
the position of the natural mortality curve requirs
independent estimates of the population trend, or trens in
recruitment. The method of Nakamura, Ohnishi and
Matsumiya (1989) takes this explicitly into account by
assuming that if the effort is held approximately constant
then the sample size will be proportional (in expectation)
to the population size. Sakuramoto and Tanaka (1989)
propose to use sightings estimates from each year for
determining the population trend. . .
　 Given this convergence on the methods to be applied, it
is appropriate to consider the precision with which the
age-dependent mortality can be estimated using a time
series of catch-at-age data and a time series of abundance
indices. Consider catch-at-age data from h years of
sampling, with h corresponding independent estimates of
population size. The moment estimator or the
age-dependent survivorship from natural mortality from
age a to a + 1 is the ratio of the total number surviving at
age a + 1 to the total number at hazard at age a , and is
estimated by:

^Sa = (Σ Nt+1 * p a+1,t+1) / (Σ Nt * p a,t - c a,t) (7)*

where Nt is the estimated population size in year t, p a,t is
the proportion of animals aged 　 a 　 in the sample collected in
year 　 t 　 , and 　 c a,t 　 is the catch of animals aged a in year 　 t 　 . The
same assumption as before is applied, that is, that
population estimates are taken before samples are caught
and that the sampling period is sufficiently short for natural
mortality to be negligible during sampling.

(7)* 　 シグマの区間がずれて表示されるので、書かなかった
けれど、両方とも 　 ｔ＝１から 　 ｔ＝ｈ-１までです。
^Sa 　 の ^ は 　 、原文では S 　 の上に乗ってます。
１９９０年デラマーレ論文(3）の 　 ~Sa 　 や~M a ~Mj 　 も同様。