Vol. 53 - Alaska Resources Library and Information Services

From the diel stations, 10% or more of the zoeae occurred below
40 m six times during night-time sampling (2100-0300) and four times
during day-time sampling (0600-1800).
When all samples were considered
together, 10% or more of the zoeae occurred below 40 m nine times during
daytime and five times during night.
More than 10% of the megalops
larvae occurred below 40 m only once during night-time and twice during
daytime sampling.
When the proportion of larvae below 20 m was listed,
the results were variable and showed no diurnal pattern.
The ratio of
daylight (0600-1800) to night-time (2100-0300) samples in these anlyses
was 1.5:1.
The ratio of daylight (0600-1800) to twilight and dark
(1800-0600) samples was 1.1:1.
Neither the diel stations nor all stations considered together provided
any evidence of significant diurnal vertical migrations of zoeae
or megalops larvae when 40 m or 20 m was used as the depth criterion for
migration.
About equal numbers of night-time and daytime samples were
used, so the resulting data should accurately describe the average vertical
distribution of larvae, especially the zoeae, which were well-sampled.
The majority of zoea larvae of both species and stages occur in the
upper 20 m of the water column (Figure 4.6 and 4.8), and this is where
most planktonic interactions involving these larvae can be expected to
take place.
The exception to this pattern was the vertical distribution of C.
bairdi zoeae on 11 May (Figure 4.7).
The sampling location for these
data was one of abundant C. bairdi zoeae, and the samples were collected
at the time of larval emergence from adult egg masses (see
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