Vol. 53 - Alaska Resources Library and Information Services

George Basin and extended over the shelf break beyond the 200 m isobath
by May and June 1978 (Fig. 6.9).
The outer shelf domain, where P. borealis larvae were primarily
found, was assigned to strata 2, 5, and 8 (see Fig. 2.21) for computer
assisted data analysis (see Section 2.0).
Figure 6.10 gives a monthly
comparison of the mean densities of P. borealis larvae in stratum 2 for
four years.
Generally, densities increase over time from April to June
from less than 500/100 m² to over 1000/100 m².
The very high values of
1172 larvae/100 m 2 given for April 1977 may indicate that P. borealis
hatched out somewhat earlier that year. Generally, stratum 2 mean densities
ranged from
250 larvae/100 m 2 in April to 720 larvae/100 m 2 in
May to 1340 larvae/100 m² in June.
The PROBES 1981 cruise, as shown
earlier in Figure 6.7, had consistently lower mean densities; 102
larvae/100 m 2 in April, 373 in May, 197 in June, and 227 in July.
These
lower densities may reflect a real decrease in abundance or a geographical
sampling bias imposed by adhering mainly to the PROBES A line (see
Fig. 2.13, middle transect).
A cross-shelf comparison of P. borealis mean densities appears in
Table 6.5 for PROBES 1978 data; no other cruise sampled these 9 strata
as extensively during May and June. Comparing strata 8, 2, and 5, the
outer shelf domain, gives a picture of relatively homogeneous distribution
of P. borealis larvae over the St. George Basin between the 100-200
m isobaths.
A comparison of the middle domain, strata 9, 1, and 6 with
the outer shelf domain shows a decrease in both mean densities (Table
6.5) and percentage of positive stations. A similar comparison of the
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