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

Always learning

By Sandy Parker-Stetter
January 21, 2016

The wet lab and acoustic science party members have over 150 combined years of fisheries experience.  People have studied a range of species, in an array of ecosystems, using most available types of scientific equipment.  This is a crazy amount and diversity of experience to have on board.

Even though the group has a lot of experience, it still happens that we make a prediction about something and the result is a bit different than we expected.  Sometimes we’re in the ballpark, like thinking we’ll catch adult hake but finding juveniles.  But other times our predictions miss the mark.  Below are a few examples of how we continue to learn, and sometimes be surprised.

(1) We saw an acoustic pattern that we thought could be juvenile hake mixed with other species.  We put in the midwater trawl, watched fish go into the net on the sonar, and hauled it back on board. 

Prediction: Juvenile hake with squid

Actual: Plainfin midshipmen and squid

Explanation: On the acoustic echograms, squid and juvenile hake can be similar.  The midshipmen were a surprise!

A basket of plainfin midshipmen. Photo credit Sandy Parker-Stetter.

(2) The midwater trawl was set on another aggregation.  We watched the sonar during fishing, seeing hake go into the net and noting that the net was not fishing near the bottom (we always watch for this).

Prediction: Juvenile hake

Actual: Juvenile hake plus 24 other species, including flatfish and rockfish (that live on/near bottom)

Explanation:  If we fish near the bottom, even if we don’t touch the bottom, the large weights and disturbance from the trawl can spook on-bottom species up and into our net!

A 38 kHz echogram showing a track (red line is the top of the net) for a midwater trawl that was not on the bottom, but contained many common bottom species. Image credit NWFSC/FRAM/FEAT.

Tagged: Winter hake survey

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