Vol. 53 - Alaska Resources Library and Information Services

Data on the timing of molt from SII to megalops larvae in 1981 show
the beginning of this process in C. bairdi and the end for C. opilio
(Table 4.5, Fig. 4.5).
Although the data do not cover the entire period
for this molt, the rate of change in the population as a whole during the
time period sampled indicates that the SII: megalops molting is about as
long as the earlier SI:SII transition. The data for C. bairdi in 1981
further show that the molt to megalops stage larvae began approximately
one month after the first SII zoeae appeared. The same situation is
indicated for C. opilio, since no megalops stage larvae were found
before 20 June.
The data presented above show an approximate 30-day period for each
of the two zoeal stages for both species in the southeastern Bering Sea.
Furthermore, the approximate 30- to 40-day period of molting in larval
populations of each species is an indication that the hatchout period is
of similar duration.
The estimates of the duration of the two zoeal
stages in the southeastern Bering Sea are in close agreement with most
of the observations of C. opilio larvae in Japanese waters (Yamahora
1965; Fukataki 1969; Fukui Pref. Mar. Exp. Sta. 1969), although some
estimates for the latter environment are for periods as brief as 19-20
days for each stage (Kon 1970).
Samples collected in early October 1980 indicate that substantial
numbers of C. bairdi megalops were still in the water column at that
time (the estimated densities from October samples ranged from 560-1370/
100 m², number of stations = 4, compared to May samples of SI zoeae
ranging from 1,800-18,000/100 m 2 at the same stations).
This comparison
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