Vol. 53 - Alaska Resources Library and Information Services

this age are non-reproducing or sterile females.
Usually females undergo
3 molts between ovigerous periods (if they produce more than one
brood) but do not molt from the time the eggs are extruded until 2 weeks
after the zoeae hatch.
The majority of Bering Sea P. borealis have only
one brood (Ivanov 1969) and it is this last age class (5.5-6.5 yr) that
supports the fishery.
Food Habits:
Perkins (1980).
Food habits of zoeae were studied by Stickney and
Preliminary findings indicate that diatoms may be a
major food source for newly hatched zoeae in Maine and the timing of
phytoplankton blooms may be crucial for early stage survival.
Older
larvae rely more on a zooplankton diet.
Paul et al. (1978) performed
prey density and feeding response experiments with Stage I (SI) P.
borealis.
Juvenile food habits received little attention. Adult diets
consist of both benthic mollusks, detritus, small crustaceans, polychaetes,
echinoderms, and protozoans, and pelagic copepods, euphausiids,
mysids and other shrimp and crab larvae (Barr 1970; Butler 1971).
Pelagic organisms are caught during diel vertical migrations when shrimp
leave the bottom at dusk, disperse throughout the water column, and
return to the bottom by dawn (Barr 1970).
Ontogenetic Migrations:
Life stage and seasonal migrations of southeastern
Bering Sea stocks are also assumed to occur.
Stage I-III zoeae remain
generally within the area of hatch but thereafter migrate to shallower
water (46-64 m) where metamorphosis occurs and they spend their first
summer as juveniles (Berkeley 1930, for Canadian stocks); thereafter
they move to deeper water to join the adults.
Ovigerous females in the
700