Vol. 53 - Alaska Resources Library and Information Services

megalops larvae of both species and first post-larval (first instar)
crabs of C. opilio.
Data on rates of larval development show considerable variability
from one station to the next once molting in the population was under
way. This is reflected in a large variance about the mean over 10-day
periods (Tables 4.4 and 4.5).
The weighted ratios are provided for
comparison in Table 4.6, which also shows the number of larvae examined
in each period.
Despite the large variance, larval stage data are useful
for pointing out several features of the larval development process
in the populations:
1) the point in time where molting to SI begins for
each species can be fairly well defined; 2) the length of time required
for the population of SI zoeae to molt to SII can be seen; and 3) differences
in timing of the onset of molting in larval populations of the two
species can be seen.
Observations (1) and (3) are generally consistent with earlier observations
on the timing of first appearance of larvae in the plankton.
In particular, data for 1978 and 1979 both show that the molt to SII was
well underway in the C. opilio population before C. bairdi larvae
noticeably began this process (Figure 4.5).
However, this pattern did
not appear to hold true in 1980 or 1981.
will be discussed later in this report.
These interannual differences
Observation (2) indicates that
most of the hatchout occurred within a period of 30-40 days, although
other factors (temperature regime, planktonic feeding conditions or survival
of only part of a year-class) also may affect apparent duration of
the inter-molt period.
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