Vol. 53 - Alaska Resources Library and Information Services

outer shelf with the oceanic area beyond the shelf break shows high
values for mean larval density and percentage of positive stations (note
that fewer stations were sampled beyond the shelf break).
Unfortunately, stratum 4 was not sampled sufficiently to complete the
matrix.
Vertical Distribution of P. borealis:
PROBES 1980 and 1981 MOCNESS data
were used for analyses of vertical depth distribution. Both unweighted
and weighted average abundance values were calculated for each depth interval.
Even though there were few stations with extremely high larval
densities at any one depth interval, unweighted (zero stations included)
values were determined to give a clearer picture of larval depth distribution.
Figure 6.11 illustrates the proportion of the total population
of P. borealis larvae at each depth interval for 1980 and 1981 PROBES
cruises.
The total cumulative percentages of larvae in each of the
depth intervals for 1980 and 1981 were 17-32% in the upper 20 m, 49-61%
in the upper 40 m, 65-75% in the upper 60 m, and 90-95% in the upper 80
m. From the values it is evident that P. borealis larvae are relatively
homogeneously distributed throughout the water column down to 80 m, with
about 50+% of the larvae in the upper 40 m and 40+% in the lower 40 m.
Distribution and Abundance of Pandalus tridens:
The earliest record of
P. tridens larvae was from samples collected near Unimak Pass in mid-
April 1977 (no larvae were found in the February-March collections).
By
late April in 1978 they were found southwest of St. George Island, whereas
in 1980 and 1981, they were first found along the PROBES A line at
stations at depths from about 150 m to more than 200 m.
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