Vol. 53 - Alaska Resources Library and Information Services

to and impact on, pelagic and benthic crab populations.
These changes
include the following points:
1. An entire larval year-class was assumed to hatch during the 3
months of April, May, and June as proportions of 20%, 60%, and 20%,
respectively (Sonntag et al. 1980).
Based on molt frequency data
of our report for larval king crab (Section 3.0), Tanner crab (Section
4.0), and shrimp such as Pandalus borealis (Section 6.0), it
appears that the majority of larvae for these species are hatched
in a 3-4 week period of April and early May and not over a protracted
period of 3 months.
Therefore the entire year-class enters the
water column during a relatively brief period of time and is not
followed weeks later by other cohorts for that year. First stage
king crab zoeae that are killed by oil north of Unimak Island in
late April, as an example, will not be replaced by other first
stage zoeae hatched in June (although they may be replaced by larvae
also hatched in April and transported to the affected area).
Since hatching seems to be a well-synchronized event among commercial
crustaceans, a major oil spill that kills a significant proportion
of a larval year-class will not be mitigated by a later
hatch of larvae after oil disperses below toxic levels.
2. An oil concentration of 0.2 mg/l and greater that was selected as
toxic to crab and shrimp larvae is too high.
Virtually all bioassay
literature pertaining to Bering Sea species is based on short
96-hr exposures (Wolfe 1977; Karinen 1981).
Models assumed that
toxic oil concentrations would persist only one to two months, and,
for such short periods, must therefore be present at relatively
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