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

Sometimes the weather wins

By Sandy Parker-Stetter, NWFSC
January 19, 2017

Although the NOAA Ship Bell M. Shimada is a formidable vessel, there are still limitations to the conditions we can work in due to safety or data quality. The winds and sea state work in unison to kibosh our best plans.

Crashing wave
Waves off the Shimada stern Photo credit: Sandy Parker-Stetter (NWFSC)

High winds and waves make deploying expensive, often heavy, gear unsafe. We don’t want our trawl, which looks like an enormous spider web, to get twisted and/or damage the net sounders or camera/sensors that are strapped to it. Side ops have the same challenges, with the CTD with its numerous sensors and the zooplankton nets. In all operations, the safety of the crew handling the gear is paramount.

38 kHz echogram with drop-outs

As wave height increases, our acoustic data quality decreases. When our echosounder sends out a downward “ping” of sound energy, it needs to hear that ping reflected back after it hits a fish (or a krill, squid, etc.). If we send out a ping, and the ship pitches (bow-to-stern, or front-to-back) or rolls (port-to-starboard, or side-to-side) too far, the echosounder doesn’t receive the return ping. That can lead to gaps (vertical white stripes) in our data called “drop-outs.” In addition to drop-outs, high seas can also create a lot of bubbles below the echosounders which can affect the sent and returned ping.

We enjoyed some great weather early in the survey but winds and seas have picked up beyond our threshold for operation. So, it’s into San Francisco to let this storm pass and then back out as soon as we can!

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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