Informe Anual de la Comisión Interamericana del Atún Tropical, 19

28 TUNA COMMISSION
the WMI in the skipjack spawning areas of the central Pacific 18 months earlier. Yel10wfin
recruitment in the eastern Pacific could also be correlated with the WMI during the spawning periodo
Yel10wfin larvae are found across the entire Pacific in waters where the surface temperatures
are 26°C and aboye. Data on the distribution ofyel10wfin larvae in aJapanese publication show that,
in the Pacific Ocean east of 120 0 W, virtual1y none are found south of the equator. The fol1owing
concentrations ofyel10wfin larvae, in numbers captured per 1,000 cubic meters ofwater filtered, were
calculated for five areas of the Pacific from data in the same publication:
between the equator and 30 0 N from 80 0 Wto 120 0 W 0.012
between 20 0 S and 30 0 N
from 120 0 Wto 150 0 W 0.031
from 150 0 Wto 180° 0.036
from 180° to 150 0 E 0.122
from 150 0 E to 120 0 E 0.204
Assuming that the yel10wfin caught in the eastern Pacific fishery are spawned north of the
equator and east of1200W, the estimated number ofyel1owfin recruits may be tested for correlation
with the WMI in this area at the estimated time of spawning. Yel10wfin recruits during the first
quarter that they enter the fishery are estimated to weigh 4.0 pounds (1.8 kg) (IATTC Annual Report
for 1985, page 66). The age at this weight ís about %yr. The estimated recruítment of yel10wfin ín
theír first quarter in the fishery for the Xand Ycohorts for the 1967-1985 períod is given in the
IATTC Annual Report for 1985, Table 11. Físh ofthe Xcohort are recruited ínto the fishery duríng the
first quarter ofthe year, and those ofthe Ycohort during the third quarter. Because the recruits are
approxímately %yr old, the numbers can be tested against the WMI three quarters earlíer, at the
time they are estímated to have been spawned.
Mean quarterlyvalues ofthe WMI forthe entíre yel10wfin spawníng area north ofthe equator
and east of1200W have not been calculated. They are avaílable, however, for nine 5-degree skípjack
areas in the central part ofthe skipjack fishery between 5°N and WN. This area comprises about
half ofthe yel10wfin spawning area, and the values of the WMI for the nine 5-degree skipjack areas
are judged to be representive of the yel10wfin spawning area. The correlations between these WMI
values and the recruitment of yellowfin were calculated, wíth the fol1owing results: X-cohort
yellowfin recruits in the first quarter and WMI in the second quarter ofthe previous year, r s = 0.498
(P