What are we doing out here, anyway? For the last ten days we’ve been running these east-west transects, roughly 35 nautical miles long, surveying the area around the continental shelf break off the northern California coast. We headed south from San Francisco on July 5 to line 17, and we completed line 40 today, June 15.

01 what are we doing here

The idea is to survey the Pacific hake population via sonar, then catch a sample to test the findings. The population data inform the management of this fish stock via the Pacific Whiting Treaty between the US and Canada. Eventually, if the acoustics can be proven to estimate the biomass accurately, the physical catch portion of this ongoing multi-year survey could be reduced or eliminated, and the fishery could be monitored and managed using sonar alone.

02 looking for fish

03 monitor in acoustics

Acoustic visualizations look like this. Here you can see a school of hake in green/yellow/orange above the sea floor at 263 meters.

04 marine mammal watch

Before we fish, we watch for marine mammals for ten minutes. If we see any within 500 yards of the ship, we wait until they leave the area.

04a marine mammal watch foggy

We do the marine mammal watch in the fog, too.

 

05 net in the water

Finally, the net goes in the water.

05b net

The net is an AMAZING piece of equipment!

05c so much mesh unwinds from the net reels, its crazy

SO MUCH mesh of different colors and sizes rolls off the net reel.

05d we also attach instruments and other things

And it’s not just the net in the water, we also attach a bunch of scientific instruments and other gear.

06ac like this giant camera

Like this underwater camera with LED lights. (We can’t see the video until we retrieve the camera.)

06b and this sonar we call the turtle

And this sonar transducer, which we call the turtle, that lets us monitor the net opening during fishing operations.

06c and these giant weights

And these GIANT weights.

07a and these huge trawl doors, like wings that widen the net opening

AND these enormous trawl doors, which fly like wings underwater to widen the net opening behind the boat.

08 aleutian wing trawl

This whole system, an Aleutian wing trawl, looks like this underwater. We usually fish between 200-400 meters deep, and as far as 800 meters behind the ship.

09a from the turtle

Here’s the view of the net opening from the turtle…I find it amazing that blips on this screen are actually fish entering the net.

10 monitor it all and adjust the depth as you trawl to catch the fish on the sonar

From the bridge we adjust the depth of the net to match the schools of hake we see on the sonar.

11 control winches here, back of the bridge

Deck crew members control the three winches from here, at the back of the bridge, constantly communicating with the officers driving the ship.

12 birds gather and wait to see what we catch

You can’t see them in this photo, but sea birds often gather and wait to see what we catch.

13 and on deck, we wait too. it can take hours to complete one trawl

We usually trawl for 20-40 minutes, intentionally catching only enough fish for our sample, ideally around 400 fish.

14 can't wait to see what we got

On deck, we wait to see what’s in the net. The acoustics are so reliable that it’s usually almost entirely hake…but there have been some awesome surprises too!

Stay tuned for more photos from the fish lab, including the work we’re doing with the hake, and some of the other weird things we’ve discovered in the ocean!