Vol. 53 - Alaska Resources Library and Information Services

MATERIALS AND METHODS
CRUISE OPERATIONS
King and tanner crab were collected by trawl and SCUBA diving during
three cruises in 1982 along the north Aleutian Shelf (Figures 1 to 3).
The NOAA ship MILLER FREEMAN conducted the June and August cruises; the
NOAA ship DISCOVERER conducted the October cruise. In June the study area
extended from Cape Sarichef on Unimak Island to Cape Seniavin. In August
this area was extended to Port Heiden. In June samples were collected
from depths up to 70 m along 17 transect lines. In August and October
collection efforts were concentrated in areas of high abundance suggested
by the June catches. Station locations appear in Figures 1, 2, and 3.
To locate areas of high crab density for later intensive sampling, the
search techniques included trawling, TV tows, diver sled tows, and
boat-tended drift diving. To locate crabs in depths greater than 20 m,
tows of 20 min with an underwater video camera and trawls of 10 min with
an 18-foot try net were performed seaward of the 20-m isobath. Shoreward
of the 20-m isobath diver sled tows and try net trawling were performed.
To collect the smallest king crab and potential prey items, boat-tended
drift diving with standard SCUBA was conducted from 1 to 20 m around Amak
Island. Additional potential prey items for the immunoassay were taken
from bottom grabs. Diving and bottom grabs also provided the large
numbers of prey items needed for the clearance rate experiment. CTD casts
provided depth profiles of temperature and salinity. Table 1 summarizes
the ship operations.
Trawl catches were processed to estimate crab abundances and to obtain
samples for several different shipboard and laboratory analyses. For each
trawl total weight was measured, and the catch sorted for the crab species
and potential prey items needed for the immunoassay. The dominant fish
species and the presence of invertebrate species other than crab were
noted. King and tanner crab were separated from the catch, counted and
measured. Individual king crab were weighed to the nearest g, their
carapace length (CL) and width (CW) measured to the nearest mm, and their
shell condition qualitatively assessed. After measurement, ovigerous
females were either given to Dr. David Armstrong of the University of
Washington for further shipboard studies or returned to the sea. In cases
where more than 10 king crabs occurred in a trawl, the crabs were flash
frozen for later processing. For smaller trawls the crabs were measured
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