Vol. 53 - Alaska Resources Library and Information Services

Bristol Bay, resultant mortality is likely to be so high that the cohort
contributes little to the juvenile year class. From this line of
thinking, it can be argued that oil pollution and mortality of larvae in
the 50-70 m central Bristol Bay region is of little consequence. From a
contrary perspective, the offshore cohort could be a vital source of
juveniles that settle to Kvichak Bay. Numbers of juveniles and repeating
year classes in this area suggest that the far eastern end of
Bristol Bay is significant to juvenile recruitment (this point should
be given a high priority in future work).
Armstrong, et al. (1983b) criticized models of oil impact on decapod
larvae (Curl and Manen 1982; Sonntag, et al. 1980) that mixed oil to a
depth of 50 m and argued that larvae would invariably move near (or away
from) the surface over a period of several days. Data from the present
study suggest such vertical movement might be a regular daily event.
The point relative to oil impacts is that a given volume of oil could be
more toxic to a population near the surface if spread rapidly in a
horizontal plane and mixed to a depth of, say 20 m. Behavior of the
larvae would repeatedly bring them in contact with this layer containing
higher pollutant concentrations.
A further ecological consideration raised by Armstrong, et al. (1983b)
is whether hatching is synchronized along the NAS and, in turn, whether
one or several cohorts are produced annually. They criticized earlier
assumptions about timing of hatch used by Sonntag, et al. (1980) to
model oil impact at the critical point of the larval stanza. Rather
than a protracted hatch over the three months of April, May and June
(20%, 60% and 20% per month of yearly total), data from 1982 and 1983
indicate that, within a wide geographic area (e.g., Unimak Island to
Cape Seniavin), the larval year class is hatched over a short period of
2-3 weeks. Since hatching seems to be a well-synchronized event, a
major oil spill that affects a significant proportion of a larval yearclass
would not be mitigated by a later hatch of larvae after oil
disperses below toxic levels. For example, first stage king crab zoeae
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