| The Midwater Assessment and Conservation Engineering (MACE) program of NOAA?s National
Marine Fisheries Service, Alaska Fisheries Science Center (AFSC) conducted an acoustic-trawl
(AT) stock assessment survey in the Gulf of Alaska (GOA) during late spring and summer
of 2013 to estimate the distribution and abundance of walleye pollock (Gadus chalcogrammus).
The survey area included the GOA shelf from the Islands of the Four Mountains to Yakutat
Bay including many associated bays and troughs at depths between 50 and 1,000 meters
(June 8 to August 9, 2013). The survey was conducted aboard NOAA Ship Oscar Dyson,
a 64 meter stern trawler equipped with acoustic and oceanographic instrumentation,
and biological sampling capabilities. The primary instrumentation for the survey was
a Simrad EK60 split-beam echosounder system utilizing five frequencies (18, 38, 70,
120, and 200 kHz) and a Simrad ME70 multibeam echosounder, with the ME70 trigger synchronized
to the EK60 system. |