Vol. 53 - Alaska Resources Library and Information Services

stations in this area where larval king crab were abundant were also
rich in phytoplankton; so much so that nets apparently clogged as
evidenced by very low volumes filtered per unit time compared to other
stations of comparable depth. Resultant calculations of high larval
densities reflect either the actual at the time in Inner Bristol Bay, or
possibly inflated values caused by inaccurate estimates of volume
filtered.
Stage IV zoeae were the most advanced larvae collected during the second
cruise through June 14. No megalops larvae were found in June 1983,
although they were present between Unimak Island and Cape Seniavin at
the same time in 1982 (Armstrong, et al. 1983b). No king crab larval
stages were found in zooplankton samples collected in mid-September
1983. All larvae had apparently metamorphosed by this date and, as
discussed in Section 3.4 on juveniles, young-of-the-year crab were
caught at this time in areas largely outside the regions of high larval
abundance.
Date of Hatch. The first zooplankton samples were collected during a
sweep along the nearshore NAS from Unimak Island to Kvichak Bay in
mid-April 1983. Few larvae were found during that first pass of the
area and additional samples were taken as the ship left Bristol Bay
between May 1 and 5. More red king crab larvae were found in this
second group of samples, indicating that a substantial part of the 1983
hatch occurred in the last week of April through the first week of May.
Hatch did not apparently continue for a prolonged period throughout the
nearshore range of the population because: 1) average densities in
April, May and June did not increase substantially (Table 3.2-1) in
subareas IL and PM; and 2) zoeal stage frequency over these months
showed a shift to later stages consistent with the molting schedule of a
single, dominant cohort. There was no apparent and substantial hatch
that occurred in late May and early June in subareas IL, PM and PH based
on stage frequencies (Figure 3.2-3). Frequency of occurrence of larval
stages in samples taken from eastern Unimak Island to Port Heiden over a
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