Northwest Fisheries Science Center

The Main Deck

Acoustic and trawl adventures in the Northeast Pacific

This portal tracks the research and sea-going activities of the Fisheries Engineering and Acoustic Technologies (FEAT) Team from NOAA¿s Northwest Fisheries Science Center.  Follow us as we use acoustics, trawling, and oceanographic sampling to learn about the Northeast Pacific Ocean.

Back deck of Bell M. Shimada
Acoustic echogram of hake
trawl catch
 

Juvenile hake

By Sandy Parker-Stetter, NWFSC
January 18, 2017


We finally found some hake, but not the adults that we were hoping to find. What we saw on the acoustics was an aggregation (i.e. a group of fish, but not necessarily swimming in unison like a school of fish) of juvenile hake. These age-1 fish, which were born last year, had an average length of 19 cm from tip of snout to tail.

Age-1 Image
Age-1 Pacific hake Photo credit: Sandy Parker-Stetter (NWFSC)

 

 

Age-1 Echogram
120 kHz acoustic echogram (-69 dB threshold) for age-1 hake aggregation we fished

 

 

The 120 kHz echogram shows the worm-y, blue-green aggregation that we saw.  From left to right, the echogram shows ~2 nmi and from top to bottom it’s ~225 m. The other two acoustic frequencies we watch, 18 and 38 kHz, also showed the aggregation very clearly. Once we identified that the aggregation was large enough (left to right) and far enough off bottom (the bright green line over top of the dark red-brown), we called the ship’s Bridge and requested to fish. 

The phone call to the Bridge brings into play many other things: preparation of our underwater video camera, starting the temperature-depth sensor that goes on the net, a watch for marine mammals, attachment of the ship’s net sounders which allow us to watch what’s going into the net, discussion of how deep the net needs to go, maneuvering of the vessel, and finally deployment of the net. Even before the net goes it in the water preparation to fish is an involved process, with Scientists, Deck Crew, Survey Techs, and Bridge Officers all involved.


Tagged: Hake, Acoustics, Winter hake research, FEAT, FRAM, Oceanography, Ecosystem, California Current Large Marine Ecosystem, CCLME, El Niño, La Niña, Climate

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