RESOURCE ECOLOGY & ECOSYSTEMS MODELING PROGRAM
Laboratory analysis was performed on 4,483 groundfish stomachs from the
eastern Bering Sea and 983 from the Gulf of Alaska. A total of 1,484 stomachs
were collected from the eastern Bering Sea. Stomach samples taken by 23
observers in the eastern Bering Sea were returned during this period.
Groundfish Food Habits and Predation on Commercially Important EBS Prey Species, 1993-96
An AFSC Processed Report summarizing the diet composition and size, distribution,
and amounts of important prey consumed by eastern Bering Sea groundfish
from 1993 through 1996 is nearing completion. Estimates of predation by
major groundfish species -- walleye pollock (Theragra chalcogramma), Pacific
cod (Gadus macrocephalus), yellowfin sole (Limanda aspera), flathead sole
(Hippoglossoides elassodon), rock sole (Lepidopsetta bilineatus), Alaska
plaice (Pleuronectes quadrituberculatus), Greenland turbot (Reinhardtius
hippoglossoides), arrowtooth flounder (Atheresthes stomias), Pacific halibut
(Hippoglossus stenolepis), and skates (Rajidae) -- on commercially important
prey during the main feeding period of May through September are provided
in this report. Diet information on butterfly sculpin (Hemilepidotus papilio)
and marbled (Lycodes raridens), wattled (L. palaeris), and shortfin (L.
brevipes) eelpouts is also presented.
Estimated number-at-age of snow crab (Chionoecetes opilio), Tanner crab
(C. bairdi), and walleye pollock consumed by groundfish predators are presented
in Figure 1 above. Pacific cod was the main predator, in terms of biomass, on
Tanner and snow crab in the eastern Bering Sea. Walleye pollock cannibalism
was the most important source of groundfish predation on age-0 walleye
pollock. Total numbers of age-0 snow crab consumed were small for 1993-96
compared to 1990-92. However, age-1 consumption was large relative to previous
years and may indicate increased recruitment from the 1993-96 year classes.
Consumption of Tanner crab of all age groups in 1993-96 was low relative
to previous years, a potential indication of low recruitment. Age-0 pollock
consumption by groundfish was relatively high in 1994 and 1996. However,
we know from survey and fishery data that the 1996 year class of walleye
pollock was above-average, while the 1994 year class was below average.
Investigations are continuing to better understand the time and space distribution
of cannibalism and the eventual effects of cannibalism on recruitment into
Auke Bay Lab