Vol. 53 - Alaska Resources Library and Information Services

difficulties in quantitatively sampling the neuston, the occasionally
high abundance of megalops larvae found there suggests that 1) some vertical
migrations take place, or 2) many megalops remain at or very near
the surface most of the time. However, it is not currently known
whether or not surface layer aggregations are common for this species,
either temporally or spatially, as they may be for the megalops of other
species (cf. Smyth 1980; Rice and Kristensen 1982).
When aggregated at
the surface, megalops larvae are particularly vulnerable to predation by
seabirds (Schneider and Hunt 1982) and to impacts from oil spills.
4.7 Spatial and Interannual Patterns of Larval Abundance
Patterns of distribution and abundance are based on estimates of
larval abundance which are highly variable, even on small spatial and
temporal scales.
Coefficients of variation for data collected in this
study were usually around 100%, whether for samples taken in rapid
succession or samples collected within a sampling stratum over a period
of three to four weeks.
This variability is typical of plankton distributions
and is a problem which must be dealt with in all zooplankton
studies (e.g., Wiebe et al. 1973; Fasham 1978).
Despite this variability,
however, it was possible in this study to distinguish certain "high
abundance" and "low abundance" areas and years using standard statistical
methods (Incze 1983).
In this section, spatial patterns of larval abundance are illustrated
for selected years and months for each species.
These periods were
selected to illustrate the general patterns of distribution and abundance
with the minimum number of figures requiring interpretation.
In
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