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

Side Operations

By Sandy Parker-Stetter, NWFSC
January 14, 2017

We’ve been running the acoustic transects (more to come on that topic) and have been stopping for side operations (aka “side ops”). The side ops are an important part of this survey as they allow us to measure attributes of the water, and collect the small creatures in it, across the survey area. For some researchers, these data are the core of their work!

ctd rosette
CTD rosette. Photo credit Jeff Bash (NWFSC)

All side ops start with lowering a Conductivity-Temperature-Depth (CTD) package through the water to measure temperature, salinity, dissolved oxygen, pH, and other attributes from the surface to 500 m (or 5 m off bottom if we’re in shallow). From the photo you can see that the CTD “rosette” also has 12 large, grey cylinders strapped it. These “Niskin bottles” can be triggered to close at specific depths, allowing us to collect water at those depths. 

We also use small nets at some side ops stations to collect zooplankton samples – zooplankton are small animals without spines (i.e. invertebrates) that, while important in their own right, are a key part of the food web as food for many fish species. If zooplankton numbers are low because of water conditions, or if there are different species present, fish and other creatures that eat zooplankton can be affected. Small stuff, but important.

Bongo net
Bongo net. Photo credit Jeff Bash (NWFSC)
Bongo sample
Bongo sample. Photo credit Jeff Bash (NWFSC)

In the last blog I mentioned we are using two types of zooplankton nets – a vertical net and a bongo net. The image shows a 333 um (i.e. micron which is 1×10−6 of a meter) mesh bongo net on the deck before deployment. The large can-shaped weight helps it to sink and keeps the net stable. While we are towing the net upwards through the water, zooplankton are collected in both sides of the net. When the net is back on deck, both samples are filtered in the lab, frozen, and saved. The small bag in the photo contains the sample from a shallow (150 m) station. Note that you can see our label floating inside!

The side ops will continue throughout the survey and provide us with an interesting snapshot of what’s happening in the California Current Large Marine Ecosystem (CCLME) this winter.

I wanted to take a moment to introduce the Science Party on this survey. In the Acoustics Lab we have Rebecca, Steve (Field Party Chief), Ben, and me (Chief Scientist). Daytime Wet Lab crew is Victor (Lead), Jeff, Cassandra, and Rachel (who is also doing a couple of special projects). Nighttime Wet Lab is in the capable hands of Aaron (Lead), Nick, and Brittney. I’m lucky to be sailing with an all-star Science Party!

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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