Vol. 53 - Alaska Resources Library and Information Services

items generally fall between 4000 and 5000 calories per g dry weight.
This similiarity of caloric values produced the parallel rankings between
soft tissue dry weight and caloric intake. Echinoderms were the exception
to the parallel ranking because their caloric value was about half the
average of the other prey items.
Whereas the dietary composition by soft tissue dry weight and that by
caloric intake are similiar, dietary composition by frequency of
occurrence differs from both of the former. In August the prey taxa rank
by caloric intake in the following order: polychaetes >> clams >> other
> crustaceans > gastropods > echinoderms. In contrast in August prey taxa
rank by corrected frequency of occurrence in this order: other >
polychaetes > crustaceans > gastropods > clams > echinoderms. In June the
rankings by caloric intake are as follows: polychaetes >> echinoderms >>
other = crustaceans > clams > gastropods; and by frequency of occurrence:
polychaetes >> crustaceans > other = clams = gastropods > echinoderms.
The different results from the frequency of occurrence and
gravimetric-caloric methods reinforce Hyslop's (1980) statement that
frequency of occurrence data suffer when prey is not readily identifiable
and that frequency of occurrence data is a poor indicator of the bulk of
food consumed.
THE FOOD OF JUVENILE KING CRAB
What are the most important items in the diet of juvenile king crab?
The answer depends upon the meaning one assigns to the large proportion of
floc found in the stomach contents. If one regards the floc as soft
tissue from largely unknown organisms that are a different set from those
visually identified and whose hard parts were weighed, then one must
conclude that the prey items comprising over 80% of the diet by dry weight
and over 90% by caloric intake are unknown. If one regards the floc as
organic matter derived from prey items identified visually and in rough
proportion to the weights determined, then one may conclude that four
items dominate the diet of the larger juvenile king crab (CL = 53-80 mm).
In order these dominant items are (1) the polychaete, Pectinaria sp, (2) a
sabellid polychaete, (3) the sand dollar, Echinarachnius parma, and (4)
the clam, Tellina sp. The polychaetes constituted more than 50% of the
diet by weight and calories in both June and August. The sand dollar was
energetically important in June but not in August whereas Tellina sp was
important in August. Juvenile king crab appear to be a predator on small,
lowly motile benthic organisms that reside at or just below the surface of
the sediment.
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